Extreme corn allergies aren’t common, but over the course of our lives we’ve happened to meet two people who have them. “Extreme” means they couldn’t eat corn, couldn’t eat corn products, and couldn’t eat any product containing corn derivatives. One of them was so allergic, she couldn’t even eat apples unless she picked them from the tree herself — apples in the store have been sprayed with wax, and some of those waxes contain corn byproducts.
Both of these people were also extremely lean, we mean like rail thin. It’s easy to imagine alternative explanations for this — if you have to carefully avoid any food that has ever been within shouting distance of corn, it might be harder to get enough to eat. But there’s no rule saying you can’t grow fat on pork and rice, and it occurs to us that if corn were somehow in the causal chain that’s causing the obesity epidemic, this is exactly what you would see.
If corn were a direct cause of the obesity epidemic — maybe if it concentrates an obesogenic contaminant like lithium, maybe if obesity is caused by a pesticide massively applied to corn — then people with serious corn allergies should be almost universally thin, or should at least have an obesity rate much lower than the general population. Our sample size of two is far too small to draw this conclusion right now, but every sample of 100 or 10,000 passes through a sample size of 2 at some point.
Easy enough to test. So, if you or someone you know has a serious corn allergy, are you really lean? We would love to know! Do you have access to the talk.kernelpanic.zero mailing list? Is there a secret r/cornwatchers subreddit? Can we send them a survey?
Corn aside, we can generalize this argument. The obesity rate in the US is about 40%. If people with an allergy to soy, fish, sesame, etc. are less than 40% obese, that implicates the food they’re allergic to. And if their obesity rate is < 5%, that’s a smoking gun.
You could also say, maybe people with food allergies have a lower overall rate of obesity, on account of their food allergies. This is probably true. Let’s say that the general rate of obesity in people with serious food allergies is 25%, instead of the 40% of the general population. But if people with serious avocado, kiwi, and banana allergies are 27%, 23%, and 24% obese, and people with serious tomato allergies are 2% obese, that’s kind of a signal.
There are some complications, like the fact that people with one food allergy are more likely to have another food allergy. But let’s not worry about that until we have the data.
One of our most counterintuitive beliefs is that the obesity epidemic may not have much to do with what we eat. But if it does, there should be some signal in the allergy cohorts.
SLIME MOLD TIME MOLD 
have a young kid with an extreme corn allergy. Very hard to navigate. Anecdote is 95% plus in his weight for his age. Probably a bad data point since he is so young. This is one of the better places to find people with corn allergies: https://facebook.com/groups/cornallergy/
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It might be that a person’s particular genetic sequence, gut flora composition, environmental history or other factor causes both the allergy and the leanness. Still absolutely worth finding though.
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For these two samples that are extremely allergic. Wouldn’t occum’s razor be that that they just eat too few calories. Especially if they are female, I would imagine they don’t want to be eating fatty meats, or other fatty food, so just accept being thin as a side effect of their diet.
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There is a corn allergy subreddit. Though it appears many people aren’t diagnosed until later in life.
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If a specific food is obesogenic, this should show up in country comparisons.
FAOSTAT has good data on consumption of specific foods by country: https://www.fao.org/faostat/en/#data/FBS
Looking at the top maize-consuming countries, many are sub-Saharan African countries with low obesity rates. Conversely, many of the least maize-consuming countries are Pacific islands with very high obesity rates. This is just vibes of course and we can’t rule out that something else is responsible for the lack of correlation (maybe maize + some specific contaminant that’s not present everywhere is obesogenic, or processed maize products are obesogenic while the data measures unprocessed maize as a staple food). I suspect if you actually plot obesity rate against maize consumption for all countries the correlation will be very weak.
However, since American food contains so much maize in everything, it’s not very surprising that people with a severe maize allergy have a very restricted diet and end up lean.
Overall I think the FAOSTAT data is worth looking into, perhaps you’ll uncover some other interesting correlations. Maybe someone else with more expertise can chime in on how trustworthy FAOSTAT data is in general.
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I know of one person with severe corn intolerance (not an allergy, but avoids corn). She is not thin, and may for all I know qualify as obese.
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Anecdotally, a college acquaintance of mine was allergic to eggs, dairy, and gluten. He ate primarily a lot of meat and rice, which had to be prepared separately by the dining halls. He was very muscular but quite lean and had to work a lot to gain weight. Another college acquaintance was mildly allergic to corn, and she was quite skinny
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A long-time friend used to have a corn allergy as a kid. She outgrew it as a teenager, evidently. I didn’t meet her until she was 19 or so. She has always been obese since I’ve known her. I recently attended a funeral where they showed old pictures including her, and as a young child she seemed to be much closer to expected weight.
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