ExFatLoss recently put out an essay called RIP Macros, where he expresses skepticism about the common three-macronutrient paradigm, saying:

I suspect more and more that the idea of “macros” is just as useless [as CICO], unless you subdivide each of the macronutrients so much further as to dilute the concept completely.

Carbs, fat and protein are definitely real, and they’re definitely a useful lens through which to view some problems. If you get too much protein, you really can kill yourself by rabbit starvation.

But this doesn’t mean that the macros are a useful lens for every problem related to nutrition. For example, we know they have basically no bearing at all on scurvy. So they may not be a good way to understand other issues, like obesity. 

ExFatLoss makes a number of good points and we encourage you to read his essay. Here is a bit of extra commentary:

Ontology

First of all, ExFatLoss is doing the right kind of work here. In the 1980s, when obesity started looking like a major problem, macros probably seemed like a promising angle. But when you’ve spent 40 years attacking a problem from the same angle with no success, maybe it’s time to find a new angle. This is the kind of ontological remodeling that you need to crack tough problems.

If you commit to a lens too quickly, it’s easier to get locked in on assumptions that might turn out to be wrong. Related to this, we like the caution ExFatLoss shows in his naming conventions:

I changed the name because I wanted it to be more descriptive of what it was, not the proposed mechanism (lack of protein) – after all, I am still not sure that’s the causal factor.

But I also chose the “ex” (for experiment) part because it conveys uncertainty, and that the diet is in flux. It’ll evolve, hypotheses will be disproven. … In a sense, it’s almost like a serial number for an experiment, and I’ve added a few new serial numbers since: ex150deli, ex150sardines, ex150choctruffle, ex225.

…

Maybe we’ll figure out what exactly makes ex150 tick, and then we can nail down a more descriptive name. Until then, I’m hesitant, because it would be speculation and I’d rather have a serial number than a name that’s just flat out wrong.

Macros are probably just too “big”. Dividing all food into three categories is pretty broad strokes, and it won’t be surprising if it turns out that these strokes are too broad to be helpful. We can equally say that dividing all matter up into four elements didn’t work very well, and chemistry progressed much better once people got a handle on the fact that there was more than one kind of earth, that there are various airs, etc. 

Phase of matter was the system of the world at one point, but today we don’t think so much about the solid/liquid/gas distinction — we no longer think of oxygen as a fundamentally different species of thing from copper. They’re not a type of air and a type of earth, they’re both elements, elements that happen to be in different phases at room temperature.

And without getting into it too much, we’ll note that reading about how macros were discovered did not inspire much confidence in them as categories.

History

The other reason we don’t think obesity has anything to do with macros is because of history. 

People ate all kinds of diets throughout history, including all sorts of “bad” diets. People tried every combo of macros, and never got obese.

Some cultures ate high-fat diets. Some ate low-fat diets. Some ate lots of carbs. Others ate almost no carbs. You name it, some culture probably tried it. 

On top of this, people were subjected to all kinds of voyages, expeditions, crop failures, sieges, economic shocks, and migrations. When you’re under siege, you eat whatever happens to be in the city, so people besieged in different places ended up eating different weird diets just to stay alive.

These various shocks gave them all kinds of dietary diseases. Scurvy is famously associated with the age of sail, but also struck on the crusades. Beriberi is often found in prisons. And the ancient Romans discovered protein poisoning while sieging Intercatia around 150 B.C.:

Their soldiers were sick from watching and want of sleep, and because of the unaccustomed food which the country afforded. They had no wine, no salt, no vinegar, no oil, but lived on wheat and barley, and quantities of venison and rabbits’ flesh boiled without salt, which caused dysentery, from which many died.

The point is that throughout time and space, people have chosen or been subjected to almost every strange diet imaginable. These did give them all kinds of weird illnesses — we know that eating the wrong combination of things can make you sick in various ways. But as far as we can tell, these weird diets never made them obese.

This makes it unlikely that obesity can be caused by an imbalance in macros. If there were some ratio of fat / carbs / protein that could make you obese, someone would have noticed in the last 3000 years, because someone at some point would have been eating that ratio. History has provided a pretty thorough search of diet-space (not totally exhaustive, but covering a lot of ground) and has discovered lots of ways that a bad diet can fuck you up. But none of those ways was obesity. 

ExFatLoss makes this same point: 

There were of course a near infinite amount of diets people could’ve consumed back [in ancestral times]. All we know is they didn’t add refined flour and seed oils, because they wouldn’t have had those. But there might’ve been carnivorous ancestral peoples, fish-eaters, maybe some near-vegetarians. Some might have lived heavily off dairy. Some ate a lot of muscle meat, others more fat. The paleolithic era lasted over 3 million years and the earth is a big place.

So if obesity is a dietary disease, you’d think that some culture somewhere would have stumbled onto it at some point. As far as we can tell, that’s not the case. Though if someone can find an example of a reliably obese culture from before 1900, we would be very interested to know. 

To us, this is strong evidence against any macronutrient cause of obesity. And in general, we don’t think obesity has to do with ANY nutritional element of food. Vitamin C isn’t a macro, but the random walk of diets through history discovered the related disease (scurvy), and eventually normal science discovered the cure and the underlying compound. If obesity were caused by some micronutrient or something, we think it also would have been stumbled upon in antiquity, and that since then we would have found the missing compound at fault.

The exception might be nutritional elements that were very rare until the late 20th century. If there’s some substance that it was hard to even get 1 mg of before 1940, but most people are eating 200 mg/day of today, it would make sense why no one had gotten fat off that substance until recently. 

This is one point in favor of the seed oil theorists, who usually blame linoleic acid for the obesity epidemic. This compound has always been in foods, but it used to be much harder to get a lot of it. So if too much linoleic acid makes you obese (we don’t think it does, but just by way of example), it would make sense that no one before 1940 would have ever stumbled on this, because almost no one before 1940 was ever exposed to linoleic acid in these quantities. Hence such images:

We said, “we don’t think obesity has to do with any nutritional element of food”. But it might plausibly have something to do with non-nutritional elements of food, like pesticides or other contaminants. Again, if it’s something no one was exposed to before the 20th century, or that no one was exposed to in such modern quantities, then it isn’t ruled out by the relative absence of obesity before the 20th century.

Symmetry

It’s easy to assume the cure and the cause will be symmetric. For example, people who believe that a low-fat diet will cure obesity usually believe that this is because high-fat diets caused obesity. We think that high-fat diets can’t have caused the obesity epidemic, because people in history sometimes ate high-fat diets and didn’t get obese. Similarly, people who believe that a low-carb diet will cure obesity usually believe that this is because high-carb diets caused obesity, etc.

But it could be that something else (FACTOR X) caused obesity, and a low-fat diet happens to cure obesity for reasons totally unrelated to the cause.

This kind of thing is common. Antibiotics cure infections because they kill the bacteria that are making you sick, not because the infection was caused by a penicillin deficiency.

Empirically, it looks like macro-changing diets (e.g. low-fat, low-carbs, etc.) don’t reliably cause weight loss. But it’s possible that some nutritive diet could treat obesity — the potassium trial essentially fits this description, since potassium is a necessary mineral. We just don’t think a nutritive diet could cure obesity because of a matched deficiency.