A Chemical Hunger – Part III: Environmental Contaminants


Only one theory can account for all of the available evidence: the obesity epidemic is caused by one or more environmental contaminants, compounds in our water, food, air, at our jobs and in our homes, that change how our bodies regulate weight.

These contaminants are the only cause of the obesity epidemic, and the worldwide increase in obesity rates since 1980 is entirely attributable to their effects. For any two people in a group, the difference between their weights is largely genetic, because everyone is exposed to similar levels of contamination. But the difference between the average weight in 1980 and the average weight today is the result of environmental contaminants.

3.1    Weight Gain in Response to Medication

We know that this is biologically plausible because there are many compounds that reliably cause people to gain weight, sometimes a lot of weight.

Weight gain is a common side effect of the psychiatric drug Clozapine (Clozaril). On average, people taking Clozaril gain about 10 to 15 pounds. This is dose-dependent — If you take a larger dose, you gain more weight — and on high doses people sometimes gain fifty or even a hundred pounds.

Weight gain is a common side effect of the psychiatric drug Olanzapine (Zyprexa). According to some sources, more than 50% of people taking this drug gain weight as a side effect. In certain populations, the rate of extreme weight gain can be as high as 90%! In one study, a group of 442 people taking Olanzapine gained an average of 30 lbs (13.7kg) after 48 weeks on a normal dose. Other studies find similar numbers — about 20 lbs after a couple weeks and about 30 lbs after a year. There’s some evidence that the weight gain is dose-dependent.

Weight gain is a common side effect of the psychiatric drug Haloperidol (Haldol). In one study, average weight gain on Haloperidol was 8.4 lbs (3.8 kg) at 3 months and 21.3 lbs (9.7 kg) at 1 year. There was a lot of variation between individuals though. If we assume that weight gain was approximately normally distributed, some back-of-the-envelope statistics suggest that about 2% of patients would gain 60 lbs or more after 1 year.

Weight gain is a common side effect of the psychiatric drug Risperidone (Risperidal). In the same study as above, average weight gain on Risperidone was 13 lbs (5.9 kg) at 3 months and 19.6 lbs (8.9 kg) at 1 year. Again there was a lot of variation, and while it’s hard to tell without the raw data, again a reasonable guess would be that some people gain as much as 60lbs. This also appears to be dose-dependent.

Weight gain is a common side effect of the element lithium (lithium), which is often used as a psychiatric medication. Almost all patients seem to gain some weight on lithium, and about half of them report serious weight gain, on average 22 lbs (10 kg). Weight gained is correlated (r = .44, p < .001) with the dosage. Some reports suggest that 20% of patients gain more than 10 kg on lithium.

Unsurprisingly from the lipostat perspective, you’ll notice that all of these are psychiatric medications. Presumably, they affect the brain. Weight gain is a side effect of many drugs, but it’s especially famous in the antipsychotics. Further, weight gain in many of these drugs is associated with enhanced leptin levels.

3.2    Mysteries

We need a theory that can account for all of the mysteries we reviewed earlier. Another way to put this is to say that, based on the evidence, we’re looking for a factor that:

  1. Changed over the last hundred years 
  2. With a major shift around 1980 
  3. And whatever it is, there is more of it every year
  4. It doesn’t affect people living nonindustrialized lives, regardless of diet
  5. But it does affect lab animals, wild animals, and animals living in zoos
  6. It has something to do with palatable human snackfoods, unrelated to nutritional value
  7. It differs in its intensity by altitude for some reason
  8. And it appears to have nothing to do with our diets

Environmental contamination by artificial, human-synthesized compounds fits this picture very well, and no other account does.

Mystery 1: The Obesity Epidemic 

People were skinny before the modern era because these contaminants didn’t exist back then.

People’s diets were “worse” in the past — full of lard and bread — because diet doesn’t cause obesity. The ~1% of people who were obese in the past were people with one of the various medical conditions known to cause obesity, such as Prader-Willi Syndrome, hypothyroidism, or hypothalamic lesions.

Mystery 2: An Abrupt Shift 

People rapidly started getting more and more obese starting around 1980 because the contaminants are the product or byproduct of some industrial process. We’re looking for compounds that were invented around 1960 or 1970, because it would probably take a few years for enough to get into the environment to start affecting us.

Alternatively, these might be compounds that had been invented much earlier, but only began to see widespread deployment around 1980. Either way, we’re looking for that abrupt shift.

Mystery 3: The Ongoing Crisis 

The obesity epidemic keeps getting worse because these contaminants continue to be produced and continue to build up in the environment. Every year they accumulate and each of us gets a larger dose. This suggests that we are looking for compounds that don’t break down easily, or at least are being introduced into the environment faster than they break down.

Mystery 4: Hunter-Gatherers 

Different groups of hunter-gatherers remain lean while eating very different diets because the human body can thrive on many kinds of food. Some of the diets are extremely high-fat. Some of them are extremely high-starch. Some of them are extremely high-sugar. Some eat an extremely varied diet, while others get almost half of their calories from a single food source. But they don’t become obese, because they’re eating fat right off the gemsbok or yams straight out of the ground, and living in grass huts.

When hunter-gatherers adopt an industrialized lifestyle, however, they become obese just like anyone else. You’ll recall that, in 1990, a team led by Staffan Lindeberg traveled to the island of Kitava and found that none of the Kitavans were obese, despite the fact that they had plenty of foods and ate a very starchy diet.

It’s true that none of the Kitavans living on the island were at all overweight. But there were actually two overweight Kitavans — both men who had grown up in Kitava, had since moved away for many years, and who happened to be visiting at the time of the study. Lindeberg managed to examine one of them, a 44-year-old businessman named Yutala, who had left the island fifteen years earlier to become a businessman in Papua New Guinea. At the time of the study, Yutala was almost fifty pounds heavier than the average Kitavan man of his height, twelve pounds heavier than the next heaviest man, and had the highest blood pressure of any Kitavan Lindeberg examined.

When he moved away from the island, Yutala was exposed to a modern way of living. More importantly, he was exposed to the contaminants of an industrialized society. As a result, he became overweight.

Yutala isn’t an isolated case. In fact, this happens with some regularity. Lindeberg notes, “an epidemic of obesity and weight gain has occurred in former traditional populations that transitioned to a Western lifestyle,” and cites a total of 17 sources to support this claim, including examples from Sudanese communities, Native Americans, Pacific Islanders, South Australian Aborigines, and the people of Vanuatu. “When humans switch from an ancient to a Western lifestyle,” he says, “they experience increased waistlines, reduced insulin sensitivity, higher blood pressure and a host of related disorders and diseases.“

Mystery 5: Lab Animals and Wild Animals 

Lab animals and wild animals are becoming more obese because they are exposed to the same environmental contaminants that we are. If they are living around humans, in or around our buildings, eating industrially-prepared foods, or the scraps of such foods, they are exposed to contaminants in the same way as the rest of us. Even if they’re not living in close proximity to humans, these compounds are probably in groundwater and drinking water.

Mystery 6: Palatable Human Food 

Lab rats gain more weight from human foods than they do from rat chow with similar nutritional properties because obesity doesn’t come from fat or carbohydrate content, but from contaminants in the food, and human food has more contaminants than the rat chow does, likely from packaging and processing.

Processed foods end up with more contaminants in them — for example, there are 4x more phthalates in Kraft mac and cheese powders than in block cheese, string cheese, and cottage cheese. Another example are these results from the FDA, as reported by the AP. In terms of explaining why the cafeteria diet is so fattening, it’s especially illustrative that grocery store chocolate cake was an extreme outlier, with concentrations of PFPeA more than 100 times higher than chocolate milk.

Doesn’t this mean that avoiding packaged and processed food should reverse obesity? We think the answer is “maybe”. There’s not a lot of research on “whole foods” diets, but the evidence that we do have is quite promising. People seem to lose a reasonable amount of weight and keep it off for up to 12 months when they’re eating largely unprocessed plant-based foods. But we should be skeptical of these results until there are more studies. While this diet lowered almost everyone’s BMI, when we look at individual results, most people remained obese or overweight after 12 months on this diet. Similar findings are characteristic of Paleolithic diets. Even when the studies are conducted by advocates of these diets, they produce very moderate benefits, in one case causing only 6.6 lbs (3 kg) more weight loss than a comparison diet across a 3-month period.

There do happen to be a couple compelling anecdotes. In 2010, Chris Voigt, the Executive Director of the Washington State Potatoes Commission, vowed to eat nothing but 20 plain potatoes (and a small amount of cooking oil) for 60 days straight to demonstrate that potatoes are perfectly healthy, and in fact nutritious enough to sustain a person for quite a while.

This wasn’t intended as a weight loss diet — in fact, 20 potatoes a day was the amount he calculated he would need to maintain his weight (2,200 calories). Despite this, Voigt lost 21 pounds over his sixty-day diet. He even had trouble eating enough — he just wasn’t very hungry. Why would this happen? Well, unprocessed potatoes are about as raw a food as you can find, and won’t pick up contaminants from industrial cooking and packaging. If Voigt was being exposed to contaminants through his everyday diet, then switching to potatoes largely cooked at home would lead him to getting a much lower dose of contaminants.

Most people are likely exposed to some of these contaminants in their diet, so eating a diet with fewer contaminants helps. But most people are also likely exposed at home, at work, and through their drinking water, so diet alone can only help so much.

Mystery 7: Altitude 

Obesity is less common at high altitudes because of the watershed. Environmental contaminants build up as water flows downhill and are in much higher concentrations as you approach sea level.

For example, take a look at this map of by-state obesity levels from the CDC:

Prevalence of Self-Reported Obesity Among U.S. Adults by State and Territory, 2018. Map from the CDC.

The Mississippi watershed is America’s largest drainage basin, covering 41% of the country. If you compare this map of state-level obesity to a map of the Mississippi watershed (below), you’ll see that every single state with obesity rates of >35% borders on a river from this watershed system. Also informative is that the three states at the mouth of the river, Mississippi, Arkansas, and Louisiana, are #1, #3, and #4 in the nation in terms of obesity rate (39.5%, 37.1%, and 36.8%, respectively).

Obesity rates are high everywhere in America, but we can see that they are higher in states where the groundwater has covered more distance, and had more time to accumulate contaminants (see continental watershed map below). States where groundwater comes from shorter river systems have a clear tendency towards lower (though still in the range of 25%-30%) rates of obesity.

If this is the case, we should also see similar patterns in other countries.

It’s hard to find good province-level maps of obesity for China, but most of them look something like this:

China has two major rivers, the Yangzi and the Yellow river. Comparing our map of obesity to a map of China’s rivers, we see that Shandong Province, with the highest rate of obesity, is at the mouth of the Yellow River. Shanghai, at the mouth of the Yangzi, is not quite as obese, but still more obese than the neighboring provinces. And in general we see that provinces at lower elevations are more obese.

There are always a few confusing outliers, of course. Why are Maine, North Dakota, and Alabama so obese? In China, why are Xinjiang and Heilongjian provinces so obese? The answer is that watersheds play a role in the distribution of contaminants, but are not the whole story.

In some cases, though, the answer may come back to watersheds after all. For example, Xinjiang province’s main watershed is the Tarim Basin, an endorheic basin that captures water and has no outlet. Rain that falls in the Tarim Basin flows to Lop Nur and stays there. The water might evaporate, but any contaminants it carried will stay in the basin.

We see similar trends in data from Iran. In the map of Iran shown below, you can see that many of the most obese provinces are near the Caspian Sea, another endorheic basin. We weren’t able to find similar maps for Russia or for Kazakhstan, two other large countries bordering on the Caspian, but we would expect them to look similar.

There are obvious and often extreme differences in obesity between people at 0 ft of altitude and 500 ft of altitude, both in the US and in other countries. The changes in CO2 aren’t enough to make any difference, but water runoff could.

It’s important to note that altitude itself doesn’t affect obesity directly. Instead, altitude is a proxy for how high an area is in the watershed, which is itself a proxy for how badly the local water supply is contaminated. This is why Mississippi is more obese than low-lying areas of California. In California the water supply hasn’t traveled nearly as far in its path to the ocean, and has traveled past fewer farms, highways, cities, and factories.

Mystery 8: Diets Don’t Work 

Finally, no diet will reliably help because obesity isn’t caused by a bad diet and can’t be cured by a good one. Hypothetically speaking, if there was a person who was only exposed to these contaminants in their food, cutting out the contaminated food for long enough would theoretically cure them. This may be what happened with Chris Voight when he cut out everything but potatoes.

Ultimately, the fact that diets don’t work very well for most people suggests that we pick up these contaminants from other sources than just our food. Probably they are also, to varying degrees, in our water, our workplaces, and our homes.

3.3    Contamination

We aren’t the first researchers who are concerned about environmental contaminants and the role they might play in rising obesity rates. But the scope of this inquiry has traditionally been limited to how contaminants might contribute to the obesity epidemic.

One review focuses on food additives, both intentional (e.g. artificial sweeteners) and unintentional (pesticides), suggesting that “environmental contaminants are contributing to the global epidemic of obesity”, and suggests that the review will be “helpful in elucidating their role in the obesity epidemic”. Another review focused on endocrine disrupting chemicals, but closes by saying, “public health officials should think of the obesity epidemic as a function of a multifactorial complex of events, including environmental-endocrine disruptors.” Yet another mentions “nutrient quality, stress, fetal environment and pharmaceutical or chemical exposure as relevant contributing influences.”

Canaries in the Coal Mine documents the rise in obesity in wild and captive animals and suggests that “the aetiology of increasing body weight may involve several as-of-yet unidentified and/or poorly understood factors.” What factors could these be? They list a couple: viral pathogens, epigenetic factors, and at the very end of the paper, “the collection of endocrine-disrupting chemicals (endocrine-disruptors), widely present in the environment.”

A statement from the 2nd International Workshop on Obesity and Environmental Contaminants in Uppsala, Sweden concluded that “the findings from numerous animal and epidemiological studies are consistent with the hypothesis that environmental contaminants could contribute to the global obesity epidemic.”

A National Toxicology Program workshop from 2012 suggests that “exposures to environmental chemicals may be contributing factors to the epidemics of diabetes and obesity.” They suggest that there is a link between some forms of contamination and type 2 diabetes, but overall, they say that there is still not enough research to draw firm conclusions.

Despite this interest, all the claims have been quite mild, identifying environmental contaminants as possibly being one of many factors contributing in some small way to the obesity epidemic. In contrast, we propose that the obesity epidemic is entirely driven by environmental contaminants. The entire difference in obesity between 1980 and today is attributable to one or more contaminants that we are exposed to in our food, water, and living spaces.

Still, not everyone today is obese. There are two reasons for this. First of all, even though everyone is exposed, some people are exposed to more than other people. If you live in an environment with less exposure, for example at a higher altitude, on average you will be less obese.

Some people are also less affected by these contaminants than other people, even at the same dose, and this difference is largely genetic. But even these people probably still, on average, have much more body fat than their ancestors did. Hunter-gatherers have BMIs of around 22 or 23. Civil War veterans in the 1890s had average BMIs of about 23 as well. If your BMI is higher than 23, you’re probably fatter than you would be without the action of these contaminants.

Sometimes it is these factors in combination. If you have a genetic resistance and you’re exposed to low levels of these contaminants, you’ll be much less obese than average.

3.4    Further Evidence in Favor of Contaminants

The difference in obesity rates between countries, as well as the differences between states or provinces within a country, is also the result of differences in contamination. Some of it will be genetic, but some of it is because some places are more contaminated than others.

Some of the strongest evidence for this comes from immigration. When they arrive in a new country, immigrants usually have lower obesity rates than their native counterparts do, but over time they become about as obese as the natives are. Looking at the trends, it appears that much of the effect of the contaminants occurs in the first year of exposure, though it takes 10-15 years before immigrants have obesity rates similar to the rates in the host country.

During the Cuban economic crisis known as the “Special Period”, obesity rates plummeted, from 14% obese to 7% obese. Normally this is attributed to the decrease in calorie consumption and the increase in exercise, as oil shortages led people to drive less and walk or bike more. But we know already that reducing consumption and increasing exercise have very modest effects on weight loss.

The average Cuban lost about 20 pounds in just a couple of years — even though in 1993, two years into the crisis, the average Cuban was still eating a very reasonable 2,099 calories per day.

Distributions of BMI categories in Cienfuegos, Cuba, in 1991 and 1995.

Food was restricted, but very few people were starving. While obesity dropped from 14% to 7%, the number of people listed as “underweight” only went from 8% to 10.3% (see above). And it’s not like they were eating all that healthy — “the primary sources of energy during the crisis were sugar cane and rice.”

Rarely mentioned but particularly notable is that food imports virtually ceased during this period. If we assume that Cuban obesity was partially a result of contaminants in their food imports, this explains the data perfectly. Alternately, we can note that fertilizer and pesticide use sharply declined in this period as well, as both were normally derived from oil, which the island was now seriously lacking. These are also potential contaminants.

One surprising fact is that the most obese countries in the world by BMI are all tiny island nations in the south or central Pacific — Nauru, Tonga, Samoa, Tuvalu, Palau, the Cook Islands, and others. Depending on the year and the source, the 10 most obese nations in the world are usually small Pacific islands. Obesity rates in these countries are not merely high, they are clear outliers. The most obese mainland nations are around 35-40% obese, but these small Pacific islands have obesity rates in the range of 45-60%. Certainly this requires some sort of explanation.

To begin with, there are some reasons to suspect that this is largely an artefact. These islands all have very small populations and are genetically homogeneous, so it’s possible that much of the difference is genetic. Polynesians also appear to be slightly stouter and more muscular than other groups, which may mean that BMI is an especially bad measure for this group and leads us to slightly overestimate how obese they are. With a better measure of obesity, their obesity rates might be more similar to the rates of other very obese countries, like Kuwait and the United States.

In addition, Polynesian countries import most of their food and eat a lot of highly processed, canned meat (famously spam), which may be more contaminated than average. It’s also notable that Nauru, the most obese (61%) country in the world, has been heavily strip-mined for phosphate. This is interesting because mining is a major source of environmental contamination. For comparison, West Virginia is an obesity outlier in the United States, and it too has a long history of strip mining. In any case, this is why Nauru imports so much food — with about 80% of the island strip-mined, they can’t grow anything there. Most of these islands are not so heavily mined, of course, but this might explain why Nauru is 61% obese and Samoa is “only” 47% obese.


92 thoughts on “A Chemical Hunger – Part III: Environmental Contaminants

    1. gleamingecho says:

      Sorry, accidentally hit enter before I was finished.

      Here’s the average height info; not sure if it’s accurate: https://ourworldindata.org/human-height

      I’m wondering if square-cube law plays in somehow. If average height multiplies by 1.03, that would mean average surface area would multiply by 1.03*1.03=1.069, and average volume would multiply by 1.03*1.03*1.03=1.092. So we should expect about a 9% increase in the average volume of Americans born between 1930 and 1980 independent of any variable other than height.

      I believe BMI takes this into account, since (I think) it is a measure of surface area to height, but it is possible that BMI downplays the effect of increased height.

      Just a thought.


      1. BMI also doesn’t take muscle mass into account at all. Fit athletes or just regular fit people are “overweight” or “obese” according to BMI despite being under 10% body fat.

        Something to consider, although not sure what impact this has. But there are definitely more people nowdays exercising and building muscle mass than did in recent past, as fitness became so much more popular with new beauty image and standards of having more muscle mass than it was in the past.


    2. Richard Meadows says:

      This is a good point. If I remember correctly, the guy who came up with BMI back in the 1830s used the second power mostly because it was a rough heuristic that fit the data, and it was hard for everyday people to calculate exponents.

      In this article, Bryan Caplan suggests that it really ought to be height cubed:

      Then I heard an episode of the Stronger by Science podcast (will link if I can find it) in which Greg Nuckols said it should actually be height ^2.5 or thereabouts.

      The effect is that BMI works pretty well for people in the middle of the height distribution, but is inaccurate for anyone on the right and left tails.

      If people have been getting taller over this timespan, that would increase the mean BMI independently of any actual changes in bodyfat percentage. Not sure how big the effect is, but it might be important to try and adjust for it.


  1. Mahmud says:

    This is absolutely amazing……so what are the ways we can mitigate this? Before lobbying the government, on personal levels how do we cull this as much as possible?

    Liked by 1 person

    1. Rodrigo says:

      Before that I’d wait until he pinpoints any particular contaminants, I was waiting the whole article for the moment when he’d actually start naming names, but alas, that’s probably for next time.

      Liked by 1 person

      1. Mahmud says:

        Sounds about right, though my mind is already on buying an air and water filter and then figuring out how to get meat and other foods with the least chemical/plastic content possible. I think it’s worth the effort to try this on myself and testify the results.

        If slime can pinpoint anything particular though, that’s even better. This is an excellent set of articles that hits on a nagging set of intuitions and suspicions I’ve been having for a while. Also i suspect this has something to do with skin quality…remember a decade ago when I was in high school the utterly horrendous skin quality of a number of the students.

        Liked by 2 people

      2. This is a great question. Yeah, we devote a whole post to each of three contaminants we suspect, because we try to make as strong of a case as we can for each. (BTW the blog has two authors!)

        In terms of filters… most water sources are already filtered (we talked to a water treatment engineer a little about this a little), and as far as we know there aren’t going to be filters you can buy that will catch things that slip through the municipal filters (we could be wrong though and would be interested to hear about it!). Eating less meat does seem like a promising step for a number of reasons. We hope to write a “what you can do about this” post at the end so stay tuned.

        We also suspect this is related to skin quality, Lindeberg’s book mentions that hunter-gatherers he studied all have perfect skin.


  2. This series of articles is interesting & and I admire you for the ambition of the project and the generally careful approach to evidence gathering. However, I would really like to see a quantitative evaluation of the simple hypothesis that this is just calories-in-calories-out. Wikipedia tells me that during the Cuban Special Period “nutrition fell from 3,052 calories per day in 1989 to 2,099 calories per day in 1993” which is an enormous change, and a seemingly straightforward explaination for why people were losing weight.

    As commentators on your prior post have noted, the 20% increase in US calories/day between 1970 and 2010 also seems quite notable and potentially large enough to completely explain weight gain over the period.

    Also: I tried to replicate your river-based theory out of sample in Germany. I used a map [1] of the river basins, a map of the states [2] and the state-by-state obesity data [3]. The data in [3] suggests that the most obese states are Hessen, Rhineland-Palatinate/Saarland and Lower-Saxony in that order, with the least obese being Schleswig-Holstein. While it is true that Lower-Saxony is at the mouth of the Weser as you would predict, Schleswig-Holstein is right at the mouth of the Elbe, and Hesse is close to the source of the Main — neither of which seem to fit the pattern. North Rhine-Westphalia is towards the middle of the pack of states despite being drained into by the whole Rhine river system.

    Thanks again for the thought provoking series of posts. I’m hoping that I’m wrong to be sceptical, because if you are right that would be an amazing discovery 🙂

    [1] https://www.researchgate.net/figure/The-main-river-basins-in-Germany-and-the-location-of-the-selected-discharge-gauges_fig1_257046991
    [2] https://annamap.com/germany/germany-states-map.html
    [3] https://www.sciencedirect.com/science/article/pii/S1570677X06000244


    1. Martin says:

      Could it be that the drinking water is sourced differently in those places?
      I’ve got the feeling that in most places in Germany the drinking water is pumped up ground water from relatively deep, whereas in the USA drinking water is mostly taken from surface water reservoirs.
      It would make sense that deep ground water has less contaminants because it’s been filtered by many layers of soil.


    2. The general rule is that toxic compounds will decrease weight and growth. Therefor the increase in obesity will be an uncommon effect of a small group of compounds. This will be produced in few places and contamination related to that, and not equally in many countries. However, the compounds will be distributed in products around the world and should offer contamination from products, that may giver higher dosages than environmental contamination at the plant, especially if it occurs in food. It is necessary to go in much more detail to evaluate this theory.


  3. You might enjoy some of the graphs in this paper, especially in the Supplementary Materials

    It’s about autism, but it shows trends in various environmental contaminants over time. Eyeballing the graphs, both glyphosate and mercury in HFCS come close to matching the “starting in 1980” pattern, although glyphosate starts a bit too late and mercury in HFCS has been declining since 2005.

    Perhaps there are others that might catch your eye.

    Liked by 2 people

    1. Bukkakeblaster says:

      It is unlikely to be glyphosate and much more likely to be the chemical cocktail they use as adjuvants/spreader-sticker in herbicide.


  4. edin says:

    Excellent series, and already cannot wait for the next part! One personal data point:

    After the pandemic when I started working from home (march 2020) that meant I wasn’t riding my bicycle 10 kilometers (6 miles) per day, which was my only exercise. Also, I stress-eated and anxiety-eated and boredom-eated somewhat since I was trapped at home. I expected to put on some weight. Interestingly, without any conscious effort I dropped from 98 kgs (216 pounds, 29 BMI) to 84 kgs (185 pounds, 25 BMI). And I’m 39 years old, it’s supposed to be more difficult to lose weight at these ages than 20s. The only exercise I’m doing is to walk in the park with my girlfriend, low tempo, 10 kms (6 miles) on each weekend day so 12 miles slow tempo walking per week. I eat as much as I like, including boredom-eating etc. The only thing that I’m consciously doing is to avoid processed food as much as possible (but not religiously, I still have some processed or packaged items; just less) and not being in the office anymore. So it was either the office cafeteria lunch or the office itself that was keeping me overweight.

    Also, it happened slowly. I lost like 0.5 kg (1 pound) per week for 4-5 months, then even slower (half as fast). I put on some weight when I went to visit my parents for a month but that can be just me hogging mommy food. Then lost again slowly after returning home. It got steady for last winter&spring, and lately I started slowly losing again. I don’t know which factor it is, but definitely something.


  5. yuk says:

    This is all very interesting. The altitude/water proxy doesn’t work for Spain though https://www.restauracioncolectiva.com/storage/FotoNota/2984-imagen-obesidad_espana.jpg

    The two most obese regions are in the northwest, and just like California they have very short rivers which shouldn’t be too contaminated, while the second less obese region,is at the end of the Ebro river, which is choke full of contamination, specially from agrifood industries.

    And two regions which get all of their water from desalinization stations (Murcia and Baleares) have a whooping 12,4 points difference.


    1. yuk says:

      Damn, I should have waited before I read to the end. Strip mining could explain why both of those regions in the northwest are higher, but then why is Cantabria 17,6% with a much bigger amount of strip mining lower?


      1. Thanks! Well, altitude is a proxy of a proxy. Strip mining does seem relevant, but it can also come down to things like, waht professions are common in those areas? What was strip mined? Does the area import or produce food? In Cantabria, do people live upriver or downriver of the mines? Or are the mines on different rivers from the main population centers? Many cities, like in California, also source their water directly from the mountains, which may explain why many cities are surprisingly lean. Wikipedia says the mining is “zinc and quarries”. It’s possible these lead to different contaminants than e.g. coal mining in West Virginia. We understand this is a lot of wiggle room for us — we just mean, the patterns should hold in general but we shouldn’t expect them to hold for every province in every country.

        We also notice that the variation in Spain is quite limited. Most of these regions are between 20-25% obese. On the US map shown in the post, almost all of them would be green or super light green. So the range of variation might be too small for us to draw much of a signal out of, so looking too close at this variation may be a dead end. We discuss this issue a bit in the next post!


    1. Lietadlo says:

      I would say that Europeans eat significantly less processed food than Americans? E.g. canned soups are basically nonexistent in Europe, most people will cook their own soups. On the other hand, they seemed very common when I was visiting US.


      1. gerard says:

        Lol french people don’t cook soup. I can assure you that most French people eating soup use industrial stuff (it’s not a best seller given the low space dedicated to it in the supermarkets, but it does exist). Making soup is *long* and it’s not typically something served for an event (ie justifiying some effort for social reasons). As of industrial stuff, it’s gaining all the time. Reasons: speed and women’s freedom. Ouch, I said it. It can’t be the reason.


  6. Setonix says:

    Interesting, and plausible argument–looking forward to the next post which may address the point below.

    How do you explain the dramatically lower incidence of obesity in Japan and Korea, two highly industrialized societies, and ones that have significant levels of environmental contamination? Both countries use very high levels of pesticide use per ha (as high, if not higher than the US/EU), and the market for organic foods is small relative to the US/EU. Additionally, while both of these countries have significant topographic variation, most of the population is concentrated in low elevation coastal regions. Do you believe genetics drives the dramatic gap seen between Japan/Korea and the rest of the industrialized world, or are there clues in the nature of the environmental contamination that exists in these countries vs. the US/EU that can explain the lower rates?


    1. Genetics is certainly a large part of it, as shown by immigrant obesity rates in the US. Even though the population mostly lives on the coasts, these countries have shorter river systems than countries like the US, so the groundwater has less time to pick up contaminants on its way to the ocean. These countries may also not use the relevant contaminants to the same degree as the rest of the world — as you mention, this is some evidence that pesticides (or at least the ones used in Japan and Korea) aren’t responsible for obesity. They may also eat less meat?


      1. gerard, straightforward multiplication is certainly not the right way to extrapolate here. Using that model, wait 100 years and over 100% of the population will be obese. I’d propose that a logistic curve would be more suitable, but it’s purely an assumption that it would fit the reality.


  7. Jack Peterson says:

    Have you seen https://www.cell.com/cell-metabolism/fulltext/S1550-4131(19)30248-7? They did a controlled study and showed that people ate more (when fed ad lib) on an “ultraprocessed” diet, and gained about 1 pound over the 2 week study. This positive feedback could easily account for the entire obesity epidemic: ultraprocessed foods make you a little bit hungrier, and if you gain 1 pound every 2 weeks, it wouldn’t take long for you to get fat.

    I think this is consistent with your broad “environmental contaminants” hypothesis — it’s just that the contaminants are specifically the ultraprocessed crap in a lot of modern foods.

    (This would also help explain why extended fasting is so successful at losing weight and keeping it off: maybe it short-circuits this positive feedback loop. Personally, I’ve always found that a 3+ day fast “resets” my appetite and general eating habits to some kind of healthy default.)


  8. Hughbjuggbjjgffv says:

    have a dumb question: why do I know people who have gone from long-term overweight to skinny? Shouldn’t this be impossible or, at least, random, according to the various mysteries and your suggested solution? But these people did it in the conventional wisdom way and kept it off

    Other dumb question: doesn’t obesity correlate with socioeconomic stuff? This seems out of step with the theory unless richer people buy nicer food with fewer contaminants. But I bet even within a single town BMI correlated with socioeconomics


    1. These are great questions. This first one in particular is one we’re really interested in. We suspect that cases where people have lost a lot of weight (which are very rare) are cases where people have seriously reduced the amount of contaminants they are exposed to. In most cases, we would expect these people to have changed careers, moved to a new living situation, or made some other major life change about 1-3 years before they lost the weight. If a 300 lbs auto mechanic in Louisiana moved to Thailand and got a job as a writer, they would probably lose a *lot* of weight — less extreme changes can make similar things happen in some cases.

      Possibly, but a lot of this is probably 1) related to what professions poor people have 2) because poor neighborhoods tend to be more likely to be contaminated than rich neighborhoods, and 3) in the US at least, because poverty is confounded with race.


      1. Hughbjuggbjjgffv says:

        Thanks for responding!

        Your theory for number 1 is extremely interesting, but it seems to suggest that people should be losing significant amounts of weight randomly all the time 1-3 years after major life changes. I don’t think I know a single person who has ever lost a lot of weight totally randomly — and this is not just post-facto narrative because most of these people I know who lost a lot of weight are pre-registering changes they’re going to make (“I’m going to start working out this New Year’s!” “I’m going to an experimental weight loss program” etc). I can believe your explanation as the reason THAT time worked as opposed to all the other times they tried to lose weight — but again, if it was completely out of their control as you suggest, I would think people would be gaining and losing noticeable weight for no reason all the time.

        But if the reason is simply “by eating ‘healthier’ foods they’re simply avoiding more phthalates” I can buy that, although other than raw potatoes you don’t seem to think that’s a simple possibility.


        1. Presumably most people who want to lose weight are often starting new plans or programs to try to lose weight, so it won’t look random — it will look like the diet or weight loss program is working. But we think this is actually downstream of a major life change. We’re trying to get some data on this now.

          There may be some cases where it’s a change in the diet, but controlled studies of diets have such limited results we don’t think it could be that very often.


      2. Bukkakeblaster says:

        Intelligence, education and wealth is going to be the answer to your mystery.

        Also corn and the shifts in chain sizes of fatty acids bred into crops. Breeding for high oleics


      3. I don’t think poverty is that confounded with race in the U.S., simply because there are not, relatively speaking, all that many racial minorities, and the fraction of them that are poor is even lower. And, too, with black people in the U.S., the obesity problem is complicated by the widespread vitamin D deficiency.


      4. TT says:

        Along the lines of question #2 from the above post, have you controlled for education when looking at the elevation data? Some of the outliers where the elevation thesis or the drainage thesis don’t seem to fit well look like they could be associated with educational status or economic indicators. Also, the lower elevation areas shouldn’t just have higher rates of obesity, they should have changed significantly more since 1980 than the surrounding areas, right? Finally, I would like to see some of the ways in which the highest obesity areas differed from less obese areas *before* our 1980 start point of the obesity epidemic. None of this would necessarily debunk the toxin theory, but I think it’s part of the story.


    2. ls says:

      I think that you know people who have lost weight because the authors were wrong about dieting not working.

      Dieting can work, if you exercise incredible self control. The questions still remains as to why staying thin now requires incredible self control, when previously it seemed to be effortless for almost everyone.


  9. Eric2 says:

    Very interesting graphs. It would be interesting to look at how different regions get their water. For example, some desert regions have now shifted to desalinized seawater. Seawater is probably low in human contaminants to begin with (they are diluted by the sea’s immense volume), and if desalinization can filter out salt it can probably filter out larger contaminants too. Have obesity rates in these countries gone down? In the Persian Gulf states, my impression is obesity has risen.


      1. George Herold says:

        I use to use a reverse osmosis filter. My limited understanding is that it of diffusion through a barrier. The amount of diffusion depends on the pressure difference and more importantly solubility (I think that’s the right word) of the diffusing chemical in the barrier material. The only example I have is a rubber balloon. Rubber balloons deflate because the air diffuses through the rubber. If you fill a rubber balloon with CO2 it will deflate faster, because the CO2 is more soluble in the rubber than air (O2 and N2 moslty)
        Aquarium hobbyist use them to clean up their water. I’m going to guess that the large macro-molecules we are theorizing about are removed to a large extent. (But of course I can’t be at all certain…) This article is kinda short on details. https://en.wikipedia.org/wiki/Reverse_osmosis But it the people in Cape Coral, Florida are notably thinner….

        Liked by 1 person

  10. Incre says:

    Have there been any studies showing that the rodent populations are more obese downstream?

    Rodents, such as mice, have a small enough roaming area that if there is more pollutants downstream that cause obesity that their would be a gradient of increasing obesity as you get closer to the mouth of the river.


  11. I was 265 pounds, 120 kilograms. As a result of diet and exercise, mostly diet, I got down to 175 pounds, 80 kilograms, and have stayed there for a few years. It was not easy, but it was not intolerably difficult.

    I think the cause of obesity is spiritual/political/cultural. And of course the cafeteria diet, with nice food being conveniently right at hand 24/7. Not chemical contaminants, but spiritual and metaphorical contaminants.l. We gain weight because debased.

    It is not that people upstream have lower rates of obesity, or that people at higher altitude have higher rates of obesity, but that people further from the cultural centers of power have lower rates of obesity.


  12. I hope that part of your investigation will be into the gut biome. As well as rising obesity, we have a rise in auto-immune disorders, from the simple (but incredibly disruptive) hay fever, to more severe diseases like asthma, lupus, MS, etc. The immune system is very very effective, and “over-active” in people with auto-immune disorders. In a society that spends more time in touch with the land, they are more likely to have a gut biome (from viruses, bacteria, and worms) that not only keep the immune system busy, but also prevent obesity. Of course, contaminants could be the reason the gut biome is disrupted.


  13. ls says:

    I have a couple of thoughts:

    You say that filtering doesn’t remove these contaminants. Could distillation remove them?

    Are there any communities that drink only distilled water, or rainwater? If you could find communities like this, and they all have much lower obesity, that could provide strong evidence for your hypothesis.

    You suspect that skin problems are related to these same contaminants. Could you check if, for instance, accutane is prescribed much more near the mouths of rivers? Perhaps you could check to see how frequently people in different areas google terms like “acne”.

    Competitive bodybuilders frequently go on extreme cut cycles before competitions. Could we check whether top bodybuilders are disproportionately likely to come from high altitude areas? Contaminated bodybuilders might find it much more difficult to cut, and thus we would expect to see very few of them at high levels of competition.

    If this turns out to be true, it could be huge. Could it be a good idea for rationalists to start investing in water filtration or distillation companies now?


    1. Good question. Distillation probably removes more than filtering but won’t remove everything, it depends on relative boiling points. So until we figure out what contaminants are responsible (we have some candidates but aren’t 100%) we can’t be sure. Also, you might have to distill it yourself, we’re not sure if we trust commercial distilled water to actually be distilled (unless it’s from a chemical supply place?).

      Not that we know of, but that is a good idea.

      We haven’t come across any acne-by-region data but if anyone finds some, they should let us know!

      Hm that’s a great question. Some bodybuilders read this, any thoughts?

      Shorting diet & exercise companies seems like a better bet, but it could take years for this idea to gain popular support, so don’t move too fast!


      1. George Herold says:

        Distillation has to remove the contaminant. Distillation basically how water vapor gets into the air. If the Human contaminant is in the rain water then all the people of the earth would show effects, and not just those that get exposed to the western diet. In fact so much stuff is removed from distilled water that drinking it is bad for you… the wrong balance of salts.


      2. How do you know filtering doesn’t remove everything? We have a ZeroWater filtered container for cold drinking water in our fridge, and though it takes longer, it removes just about all measurable TDS (total dissolved solids). (As you may know, electronic TDS measuring devices are widely and inexpensively available.) If those devices measure simple atoms and diatoms– elements like chlorine and lead– then surely they would be able to measure more complex molecules like the pollutants we’re talking about.


  14. George Herold says:

    Very nice, I’m enjoying this series. I want to push back a little on your ‘it’s in the water’ idea. I’m not saying this idea is wrong, just that it doesn’t look like a slam dunk to me.
    1.) If it’s in the water then all the wild animals drinking the water should show some effect. And not just those animals that are eating ‘human’ food. (by human food I mean stuff from the processed western diet,) So that would be rats, pigeons, pets… Are deer fatter in Mississippi than Vermont?
    2.) If it is in the water, I’m not sure watershed size makes that much difference. The question is how it gets into the water. One could point to industrial waste dumped into the water, or agricultural run-off. Those things happen at the source, and then the water continues to the sea, I don’t see how traveling a long distance allows it to pick up more of the contaminant . You talk about ground water. I would think that ground water would be mostly clear of any human contaminant (HC). Ground water flows beneath the ground. Unless it flows through some land fill, I don’t see how it picks up HC. According to this https://www.groundwater.org/get-informed/basics/groundwater.html, about 50% of us drink ground water. It would be interesting to see if there was any difference in obesity that was effected by the water source.
    3.) People in low lying areas (and near water) show more obesity. As an alternate hypothesis, to explain this, perhaps these people eat more fish in general, and it is the fish that are accumulating the HC in their bodies. Fish, (especially those near the top of the fish food chain) are very good at concentrating contaminants. (I don’t think this idea fits all the facts either, so just an alternative.)
    4.) If it’s in the water how do you explain the rats getting fat on the cafeteria diet?
    5.) I don’t see how strip mining matters, sure it puts a lot of bad stuff in the water, but how does it put in more of the HC (Human Contaminant)
    6.) Obesity and wealth. At least in the US I think there is a strong correlation between these two, perhaps the population you see near the Mississippi are poorer on average. It’s a tricky political topic to talk about obesity and wealth, is that why you have mostly ignored it?
    So again I’m not saying that it’s not in the water, just that at this point I think it would be wrong to focus all our attention there… we really don’t know what it is.

    I had this wonderful (and most likely BS) idea for the altitude effect. Higher altitudes get more cosmic rays. Perhaps part of our cell mechanisms that deal with cosmic ray damage also work to reset ‘get fatter’ set point in our bodies. I know, simply wild speculation on my part. And I’m basically clueless about cell and molecular biology… It did make me think that we could look and see if airline pilots and attendants were less obese, and if they got fatter once they stopped flying. Do pilots retire and get fatter? (Oh the idea is wonderful, because if I could point to some potential good in cosmic rays, then people might also embrace nuclear energy (I picture people hugging reactors to get their radiation dose.) and we’d cure global warming, energy and obesity in one fell swoop.)

    I also wanted to link to this 2002 paper. http://www.chemicalcalories.com/assets/pdf/academic_paper.pdf She has also written a few books on the subject. https://www.amazon.com/Paula-Baillie-Hamilton/e/B001HD0Y46%3Fref=dbs_a_mng_rwt_scns_share
    I’ve read none of them.


    1. Mahmud says:

      ” I would think that ground water would be mostly clear of any human contaminant (HC).”

      I don’t think so. https://www.sciencedaily.com/releases/2020/10/201026153939.htm

      Unfortunately, potential endocrine disruptive have made it into ground water. There’s a new book out about this by shanna swan. Anyways she says plastics seem to be making boys penises smaller, the distance between their penises and anuses shorter, and reducing T levels. I think lower T corresponds to higher fat storage so Im guessing there may be a connection.



      1. George Herold says:

        Ok thanks. Micro plastic in ground water. I guess plastic containers and plastic trash follow with the western diet.


  15. This comment probably belongs on the previous post, but discussion seems to have moved here, and I’ll move with it.

    You’ve done a good job arguing that the culprit behind the obesity epidemic isn’t anything nutritional, like added sugars. However, I feel that you’ve done little to refute the theory that hyperpalatable foods break our lipostat/cause us to overeat beyond what our lipostat would normally recommend. This could look a lot like the contaminant theory because both mainly affect people who eat processed foods, and both involve the appearance of the lipostat being mis-set.

    It seems like the best counterevidence you provide to the hyperpalatability theory is that we eat “merely” a few hundred more calories now than we used to (though it seems to me that, over the course of many years, this could cause enough weight gain to explain the obesity epidemic). Is there further evidence that I’ve missed/you’ve omitted which causes you to prefer the contaminant theory?

    (Also, thanks for this sequence of posts, it’s really excellent!)


    1. Not to be glib, but what evidence is there that hyperpalatable foods are behind the obesity epidemic? It also doesn’t seem to fit the general pattern of obesity. Did food abruptly get good around 1980? How would this explain things like the altitude effect? There seem to be a number of patterns that fit if obesity is caused by contaminants and that don’t fit if it’s caused by hyperpalatable foods.


      1. saprmarks says:

        Much of the same evidence you present as implicating a contaminant seem (to me) to equally well suggest hyperpalatable foods. For example:

        1) Palatable human foods causing humans and rats to gain weight (apparently because they’re overeating?)
        2) Hunter-gatherers not gaining weight
        3) Animals living in proximity to humans gaining weight (because foods that taste very good to us might also taste very good to other mammals)
        4) Continuing growth in obesity despite dietary changes (since we might expect food to get tastier over time, even despite using less sugar, etc.)

        Now, the above don’t help distinguish between hyperpalatability and contaminants (or do you disagree?), but they do help make *both* hyperpalatability and contaminants looks better than the other alternatives. In terms of evidence that distinguishes these, I see:

        5) The fact that people now eat more calories than before (weakly favors hyperpalatability, unless the contaminant acts via increasing appetite (in which case it would be *really* hard to distinguish from hyperpalatability))
        6) The thing from the Hungry Brain where people given ad libetum access to bland nutrient sludge eat exactly enough to maintain their weights (if they’re healthy) or eat very little without feeling hungry and lose a lot of weight (if they’re obese). (Weakly favors hyperpalatability, same as (5).)
        7) Common sense and anecdotal experience — most people I know complain that they gain weight when they’re around a lot of delicious food for a long time. It’s possible that we’re all wrong that the yumminess is what causes the overeating, and actually we are just blaming our contaminant-induced appetites on the yumminess, but I’m still gonna call this strong evidence favoring hyperpalatability.

        8) The epidemic only started in 1980 (favors contaminant, but only weakly because it wouldn’t be that surprising if food started getting really good around 1980)
        9) People are fatter in lower altitudes (this might favor contaminants, depending on the answer to this question, which I meant to ask you anyway:

        Have people in lower altitudes gotten fatter relative to people in high altitudes since 1980? Or have they always been fatter, and starting in 1980 everyone in both high and low altitudes started getting fatter together? Because if it’s the latter then it’s strong evidence for a contaminant, but if it’s the former than it just means that there’s a separate thing going on where people in lower altitudes are fatter and it has nothing to do with the obesity epidemic that started in 1980.)

        Oops, that got long. Thanks for your attentiveness to annoying comments like these!


        1. lol no worries

          > Now, the above don’t help distinguish between hyperpalatability and contaminants (or do you disagree?), but they do help make *both* hyperpalatability and contaminants looks better than the other alternatives.

          Hard agree, the strongest conclusion of the piece is that “traditional” explanations of obesity don’t make sense. This evidence makes a number of alternative theories look plausible, since they fit with these data.

          > unless the contaminant acts via increasing appetite (in which case it would be *really* hard to distinguish from hyperpalatability)

          The contaminant(s) almost certainly act by raising the lipostat set point, which among other things would increase appetite… so yes they might look rather similar in many ways

          > The thing from the Hungry Brain where people given ad libetum access to bland nutrient sludge eat exactly enough to maintain their weights (if they’re healthy) or eat very little without feeling hungry and lose a lot of weight (if they’re obese)

          Maaaaaaaaybe. A few thoughts. This study was performed in 1965, which means that it was decidedly pre-obesity-epidemic. Those people probably were not obese for the same reason(s) people are obese today, so the same rules may not apply. In addition, studies from 1965 are not known for being super reliable. If memory serves, we looked for the original paper for this study and couldn’t find it. If you can find it, we’d be interested in taking a look. But in summary we shouldn’t conclude too much from one study from 1965 when we can’t find the paper and it predates the phenomenon we’re interested in.

          > Common sense and anecdotal experience — most people I know complain that they gain weight when they’re around a lot of delicious food for a long time.

          There’s a long history of commonsense explanations being really wrong, and this looks like one of those cases to us. Overfeeding studies in particular seem to provide a controlled version of “around a lot of delicious food for a long time” and they don’t lead to long-term weight gain!

          > it wouldn’t be that surprising if food started getting really good around 1980

          We think that would be weird. People have always liked tasty food. To quote from Part I, “Doritos were invented in 1966, Twinkies in 1930, Oreos in 1912, and Coca-Cola all the way back in 1886.” If you look at historical recipes, they used a lot of lard and butter.

          > Have people in lower altitudes gotten fatter relative to people in high altitudes since 1980? Or have they always been fatter, and starting in 1980 everyone in both high and low altitudes started getting fatter together? Because if it’s the latter then it’s strong evidence for a contaminant, but if it’s the former than it just means that there’s a separate thing going on where people in lower altitudes are fatter and it has nothing to do with the obesity epidemic that started in 1980.)

          Interesting question. For most of history, almost no one was obese, about 1% of the population or less. Unfortunately historical data is a little spotty on finer-grained details, but there’s certainly no evidence that people at lower altitudes were at all heavier than those at high altitudes. You could maybe look for turn-of-the-century photos from different cities, but almost everyone will look lean, so… probably more evidence in favor of contaminants.

          In addition, the theory needs to explain the variation between nations. Why are Kuwait and Jordan so obese? Do they have tastier food than Canada and Australia? Can they not afford delicious cakes in Japan, Korea, Switzerland, Denmark, Italy, Sweden, Portugal, etc…? This seems like a place where hyperpalatability seems to fail but contamination could potentially explain the difference.

          In addition, we feel confident in the contamination theory because we feel we were able to make very strong cases for three contaminants in particular. So stay tuned for Parts V, VI, and VII. Also, there are a couple of surprising results we will share in later parts which match contamination very well. So stay tuned for Parts VIII+!


      2. saprmarks says:

        Thanks for your detailed reply!

        I’ve found a pdf of the 1965 study cited in The Hungry Brain — I’ll email it to yinz* now.

        (*do you have a preferred form the second person plural?)

        Your point about inter-country comparisons favoring the contaminant hypothesis is well-taken. And of course facts about particular proposed contaminants can move the needle as well. So I now better understand your preference for contaminants over hyperpalatability. Cool!

        Liked by 1 person

      3. > Can they not afford delicious cakes in …

        Affording might not be the right question. If, for purely historical/cultural reasons, they happen not to have built up a habit of importing/making hyperpalatable foods in the first place, they may not be on the vicious cycle of craving. (Or on it to a lesser extent). If eating a McDonald’s cheeseburger makes you want to eat more, but it’s not culturally normal for your people to eat McDonald’s cheeseburgers (and especially if eating one is a little more expensive or requires going a little more out of your way to obtain), eating one once or twice may not be enough to overcome the counteracting factors. You go back to eating your regular, somewhat less tasty food, and become part of the reinforcing culture that prevents those around you from eating McDonald’s cheeseburgers.


    2. I would also point out that hyperpalatability, apart from being testable (the number of historical cookbooks around is amazing, as is the skill at “living history” in cooking) would not explain why lab animals, zoo animals or horses were getting fatter. Surely we haven’t been devoting lots of energy and taste-testing to improve the flavor of lab chow or fodder.


  16. EBM says:

    I really appreciate this series so far! I hope you include some specific predictions in the upcoming articles, so you (and others) can evaluate and refine the theory going forward.

    As a lifelong fat guy who has a lot of difficulty dieting, I’d love to discover that there’s some contaminant to blame. However, so far, the theory that has seemed the most elegant and compelling to me is the “food reward” theory described by Guyenet in The Hungry Brain, criminally oversimplified to “food tastes good so we eat too much”, or perhaps “food tastes so good it somehow damages the lipostat”. My impression is that extremely convenient and ultra-palatable foods are relatively recent inventions, and if you’re constantly optimizing food to make us want to eat it, you’ll get an ongoing rise in obesity.

    The food reward theory seems to have an answer for many of the obesity “mysteries”. In olden days, you couldn’t get fat unless you had access to convenient, ultra-tasty food. In the 70s and 80s, we learned how to produce and distribute a variety of cheap, convenient, superstimulating food, and we’ve been getting better at it ever since. Hunter-gatherers don’t have variety or convenience, and even their “tasty” or “unhealthy” food is not anything that appeals to the Western diet. (Who drinks a pint of honey? Who wants a slab of unsalted animal fat?) Animals get fatter the more access they get to palatable human foods (or perhaps if they are subject to a parallel optimization process, i.e. cat food is becoming ultra-palatable to cats). All diets work equally not-very-well because they all involve restricting *something* that we otherwise would like to eat, but the particulars don’t much matter. The only remaining mystery is altitude, but although I’m very intrigued, it seems like one of the weaker bits of evidence so far, for reasons suggested by other comments.

    The frustrating thing about the food reward theory is that it points in the same obvious direction as so many other theories: stop eating junk food. Everyone already agrees with this! If you think the problem is seed oils or sugar or fat, whether you believe in the paleo diet or whole foods or low-fat, cutting out ultra-processed foods is a huge part of the answer. And, unfortunately, it seems like the same is true for trying to cut out obesogenic contaminants. How can you test your theory against these others, when they’re all so correlated? Where’s the one weird trick that would cut out the contaminants but retain most of the stuff we like?

    I dearly hope the contaminant theory is true. To my knowledge, the food reward theory doesn’t have a clearly established mechanism for *how* excessive food reward would damage the lipostat. What if the problem is not deliciousness itself, but just some chemical that we can identify and replace? Could we have a future where you can eat whatever you want and stay thin (because you don’t *want* excessive food anymore)? I want that!


    1. The problem I have with the Food Reward theory is that prepared food is not, to me, dramatically better than home-cooked food, and it’s often less so. Doritos are good but not that great, and as our host has pointed out, they and many other forms of junk food long predate the rise in obesity. MSG is also associated with Asian food of one sort or another, but the Chinese and Japanese have no obesity problem. (Of course, it’s possible that it’s mostly a Chinese-American food component, not Chinese itself.)


  17. Tummler says:

    Perhaps municipalities switching from aquifers to rivers as their source for drinking water and vice versa may serve as a natural experiment to test your watershed hypothesis.

    It’s my understanding that it may take decades, if not centuries, for surface water to travel to and then through deep aquifers before it is pumped out fot consumption. Therefore, water sourced from aquifers may have a different concentration of the hypothetical contaminant compared to water sourced from rivers.

    One possibility for this natural experiment would be small Midwestern towns that switch from locally sourced water pumped from deep wells to rural water systems, which often source water from rivers far away from the town.


  18. Matt says:

    Given the example of rats eating chocolate cake getting fatter than eating unprocessed foods, it should be very simple to prove or disprove the chemical contaminant theory with lab rat experiments by adding these contaminants to uncontaminated food. Actually, I hope someone’s already done this study and it will be shown in Part IV+, since it seems like a pretty trivial way to validate these assertions.


  19. John C says:

    Why are you dismissing polyunsaturated fat (PUFA) and linoleic acid so easily? It seems to fit your contaminant hypothesis really well IMO except it’s actually delivered via diet and not environment. I didn’t see it explained away specifically in any of the diet pieces in parts I and II.

    >If you look at historical recipes, they used a lot of lard and butter.
    Indeed, and the introduction of PUFA in industrialized snacks and home/restaurant cooking correlates very well with the rise in obesity (correlation isn’t causation of course): https://youtu.be/7kGnfXXIKZM?t=897

    >In addition, the theory needs to explain the variation between nations. Why are Kuwait and Jordan so obese?
    PUFA strikes again in Kuwait: https://fireinabottle.net/the-anti-french-diet/

    I can’t seem to get to the raw data like fireinabottle does, or else I’d like to look back in time at Kuwait’s unsaturated fat intake and obesity rates.

    I’d also love to find a source of animal feed ingredients over time to find out if increasing PUFA in feeds can explain mystery 5. On that topic, we’ve known for over 100 years that American pig fat is inferior to European pig fat due to what the pigs are finished on: https://fireinabottle.net/polyunsaturated-fat-pufa-in-pork-and-chicken/


    1. We weren’t aware that this was a popular explanation when we wrote the piece so we didn’t think to address it. We’re considering writing another interlude on this topic specifically. Like you say, it may actually be compatible with the contaminant explanation — vegetable oils may be especially high in the relevant contaminants as a result of their processing.


  20. I was expecting an answer similar to “hyperpalatability” mentioned above.

    Why would it kick off in 1980s? Could be something like the proliferation of artificial flavours, novel processing techniques.

    But for me it is MSG that makes food more palatable far more than other additives like salt, sugar, artificial flavours. I’d look at the history of MSG usage in western snack foods. I suspect that it is now also widely used in pet foods and wildlife who have had contact with humans (fed by them or scavenged) may also develop a taste for it.

    But ultimately it isn’t a single substance but a carefully crafted layering of flavours – salt, sugar, umami (MSG), fat, acid – that makes food delicious “more-ish” and perhaps we have just got too good at the culinary arts?


    1. We don’t find hyperpalatability to be a very likely explanation, in part for the reasons mentioned above. There’s a large amount of variation in obesity between nations. Some of it is genetic but not all of it, and it doesn’t seem like it maps onto which countries have the most delicious food. Certainly with globalization, rich countries can import pretty much whatever foods they want, but there are many rich countries that are relatively lean.

      There are also some details coming in future posts that seem to provide evidence against hyperpalatability. To name just one, there’s a large amount of variation in obesity between professions. This seems weird because it’s not like some professions have access to tastier foods. So what is going on here? Contaminant exposure explains this well and hyperpalatability does not.


      1. I don’t think it’s the national cuisine that has to be delicious, as everyone on earth these days has access to affordable MSG laden snacks and sugary soft drinks. Perhaps you might even find that in countries where the main sources of nutrition are bland, consumption of junk food is higher. In many developed countries obesity is associated with lower socio-economic status, as is junk food consumption.


      2. I made a table of obesity rates (roughly eyeballed – not accurate) of countries grouped along geographic/ethnic/cultural grounds. Yes I’d agree that the most delicious (or least bland) food is found at the bottom of the table. So perhaps while in Asia they form part of the regular cuisine, in other parts of the world we seek these additives (spices/MSG/salt) in snack food that is in addition to our regular diet.

        1) Pacific Islands >50%
        2) USA 36%
        3) Turkey and Middle East ~33%
        4) Australia/NZ/Canada/UK ~29%
        5) Latin America ~27%
        6) Europe + Israel, Iran ~25%
        9) Central Asia ~17%
        7) Africa ~10%
        8) China/SE Asia ~5%
        9) India/Bangladesh/Sri Lanka ~4%


      3. Steve says:

        What about unleaded gas and the huge difference in professions? Cops, fireman, construction workers are all on the higher end of obese and they sopend most of their time in a vehicle or around belching vehicles.


  21. I don’t think it’s terribly likely that they add MSG to pet food, but either way, I think it’s really, really unlikely that they add it to what they feed lab animals, zoo animals and horses, so I suspect MSG is not one of the main culprits.


  22. Michael Eaton says:

    What about Hawai’i? An examination of what makes Hawaii both similar to and different from other places is an opportunity to examine the mysteries under a relatively unique collection of geographic and demographic conditions.

    For example, you cite Colorado as an example of a place with relatively low obesity rates and how that serves as an example for the Altitude Mystery. Yet both the obesity map above and in Part I both illustrate that Hawai’i, whose population lives at predominantly low altitudes, is comparable to Colorado. This appears to be an outlier.

    Hawai’i also runs counter to the observations about the Pacific Island nations you cite with the highest global obesity rates, in spite of the relative genetic similarities between native Hawai’ians and other pacific islanders.

    Interestingly I think that this apparent outlier actually serves to reinforce some of the ideas that you are bringing to the table rather than confounding them. First among them is that Hawai’i has some of the cleanest, purest water in the Unites Sates due to the unique geology of their aquifers:


    Click to access B.17w-USGS-Ground-Water-in-Hawaii.pdf

    If the proposed mechanism for the altitude distinction has to do with the opportunity for groundwater to absorb contaminants, then it might be interesting to do a comparative analysis between groundwater in Colorado and Hawai’i, respectively.

    The other thing that makes Hawai’i an interesting case is the unique genetic diversity of the state. Per https://www.census.gov/quickfacts/HI, you can see that as of 2019, Hawai’i is roughly 10% pacific islander, 25% caucasian, 38% asian, and 25% mixed ethnicity. I do not know to what degree obesity data for Hawai’i might be broken down by ethnic group, but given the observations about pacific islanders and also Japanese elsewhere in this series, it creates an interesting opportunity to examine genotypes that share a very isolated set of geographic and geological characteristics.


  23. Cass says:

    This research is extremely interesting to me, as I’m someone that’s gained about 100lbs since starting antidepressants in 2016.
    Growing up I had the tendency to be chubby, but for a few years before starting the meds I stayed a healthy weight with no effort. I’ve tried switching medications and eating various diets to lose my current weight- no dice.
    In your studies have you found any evidence of gastric bypass working long-term for those suffering from antidepressant-induced weight gain?
    Unfortunately I can’t come off my meds currently and I don’t except to be able to do so in the future either.


  24. Jonathan says:

    I think it is usually a mistake to assume anything has only one cause, when most major changes result from multiple causes. I am very much enjoying the work you guys put in. Great stuff!

    Another variable you might look into is the amount of time people sit in chairs. Up until recently, people didn’t sit very much, and when they did it was a squat. I believe the data is compelling in regards to the obesity epidemic. New Scientist did a story on it I believe. Essentially, looking at the rate of exercise vs leisure in different cultures and time periods may be very misleading, as most calories may have been burned merely by standing and squatting for long periods of time.


  25. Iconoclast says:

    This is a fascinating series and I can’t wait for the grand reveal! I am really appreciating your rigorous and open minded approach to this very complex topic.

    One thing I recently learned is that there is less deuterium in water as one goes up in altitude, with sea levels having the highest concentration. Deuterium is of course a part of heavy water and occurs naturally in tiny proportions. Apparently deuterium has a biological effect (it makes sense if you think about it) and there is a group of scientists that is quite interested in the effect of deuterium on cancer. In short, deuterium messes up the proton pump on the inside of our mitochondria that is the heart of cellular respiration. You should check out the work of Dr. Laszlo Boros and his associates. He has a YouTube channel with some of his talks. There is one of his lectures where he actually shows a really nice animation of the “nanomotor” that is the proton pump in the mitochondrial inner membrane.
    The hypothesis is that mitochondrial dysfunction is a huge contributor to cancer formation, as per Dr. Otto Warburg’s hypothesis from back in the 1930s.

    Anyway, since mitochondrial function is such an essential part of metabolism, perhaps it may have some effect on obesity before it goes and progresses to cancer. It may perhaps explain some of the correlation of obesity with cancer. I am not aware of deuterium increasing in the environment since the 1980s, but perhaps this should be something to be researched?

    Even if it doesn’t turn out to appear related, I found it a fascinating and not commonly discussed topic.


  26. Phoenix Girl says:

    How about all of the new indoor lighting that popped up in the 1980’s like halogen and compact fluorescents? The majority of people no longer spend much time outside being exposed to the array of light spectrums from the sun. It also seems to me that industrially processed oils are not compatible with our ancestral lineage of eating fats from animals. Fat cells seem as if they do not know when to stop growing.


  27. antonmaier says:

    Lets say fat gets metabolized through exhaling it as co2. If there is less CO2 in the air, blood CO2 should be reduced because of faster CO2 diffusion into air. Arguing from Chemical equilibrium.

    “During sleep at HA [High Altitude], the levels of CO2 in the blood can drop very low and this can switch off the drive to breathe. Only after the body senses a further drop in O2 levels breathing is started again. Periodic breathing is thought to result from instability in the control system through the hypoxic drive or the response to CO2. ”



  28. Nate123 says:

    I’m not sure if anyone mentions this yet, but it seems that our body is storing these environmental toxins in our adipose tissue to protect our organs from contamination. Fat storage in modern society seems to be a defense mechanism or mitigation of the detrimental effects from the toxic loads we face today.


    1. Nate123 says:

      The excess contaminants get lodged in our tissues, stuck in our blood and lymph and it has to go somewhere or else we would get sick/ die. People who are not obese have the ability to process this crap but overtime, it will lead to weight gain once your body has trouble pushing this stuff out. With the introduction of highly palatable foods high in fat + carbs like cookies, cakes, French fries, msg, additives, etc, also contributes to weight gain imo.


  29. GN says:

    You mentioned above “Why are Maine, North Dakota, and Alabama so obese?”

    Well, Maine has finally started studying their water for PFAS. WaPo article from April of 2022 details an organic farm that had to shut down due to contamination from water they were offered that was lousy with the stuff. Similar piece about the same farmers on Maine public dot org. Per Maine Farmland Trust: “Maine is one of few states that has established screening levels to assess the level of PFAS contamination for products such as meat and milk (Maine does not yet have screening levels for any plant sources).”

    They’re also checking public drinking water some sources are exceeding the 20 parts per trillion Maine has set as the allowable limit and some have PFOA above the federal guidelines. (Bangor Daily News, July 9th 2022) https://www.bangordailynews.com/2022/07/09/mainefocus/pfas-in-central-maine-drinking-water-joam40zk0w/


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