Why has the Incidence of Obesity Exploded in the US? Some possibilities

The obesity epidemic is a topic that interests a lot of people and generates considerable discussion online. I want to expound on what I believe to be the main reasons for the obesity epidemic, especially in America.

I disagree with the ‘slime mold’ or chemical theories of obesity. This does not mean it’s wrong, just less probable than more obvious explanations. I think it boils down to hyper-palatable caloric-dense foods, obesity being underdiagnosed in the past, the boom in preventive care (which is possibly ineffective and expensive), and the decline of smoking. I don’t think sedentary lifestyles explains it either. Gym attendance has surged over the past two decades, but obesity has gotten worse.

As anyone who has driven by a construction or road work site and seen big overweight guys in reflector vests, or hired overweight plumbers or overweight U-Haul movers, it’s not like blue collar workers are slimmer than sedentary white collar workers. It’s more likely the white collar guy has a gym membership but is still overweight. Physical activity burns pitifully few calories, and it may not even work at all. Additionally, I don’t think body positivity or fat acceptance are to blame, because revealed preferences (e.g. demand for weight-loss drugs) would seem to suggest that overweight people want to lose weight, similar to how many short people want to be taller even in spite of ‘short pride’. Similarly, ‘World AIDS Day’ does not imply choosing to live with AIDS when effective treatments are available that can put it in remission. I also think Covid gets too much blame. Obesity was already well on the upswing before Covid, but Covid made it worse. People actually blame gym closures during Covid for obesity, yet the graph above clearly shows that gyms do not help. Binging on food during quarantine due to boredom contributed way more to obesity than gyms being closed.

But what about Asian countries? What are they doing right to have such low rates of obesity? What can ‘we’ Americans learn from them? Not so fast. Their ‘secret’ to thinness is less muscle, not less fat. Whites and blacks are fat but also stronger and more muscular too, which is why they tend to dominate sports, compared to Asians. Indeed, this is evidenced by much lower FFMIs for Asians:

The possibility of obesity being underdiagnosed in the past deserves more consideration. The post-1980s ‘explosion’ of obesity also tracks the explosion of the healthcare and health insurance industries. As healthcare has become more expensive and as Americans get older, it necessitates more insurance, and hence more doctor visits and diagnosis of obesity. Weight is closely tracked for pricing insurance premiums, compared to 70 years ago when insurance was not as big of a deal as it is now. Also, photos from 60+ years ago of outwardly appearing non-overweight people are possibly misleading, because loose fitting clothes are good at hiding weight and you cannot tell by just looking at someone the difference between, say, a 23 vs 25 BMI (which is borderline overweight), compared to precise body measurements at a doctor’s office for insurance purposes, drug dosing, or annual physical.

Same for the rise of health and fitness industries, especially since the mid 2010s due to the popularity of social media, which has also made people more aware of obesity and self-conscious.

The decline of smoking is probably another major factor, inversely tracking the rise of obesity. Junk food is effectively a ‘safer’ form of drugs, providing a similar dopamine rush and boost as drugs or smoking, but legal and perceived as more safe. Food companies know their products are addicting and have optimized food for taste and palatability, which means more calories, similar to the process of purifying drugs for increased potency. It’s not just ‘junk food’, but anything that is not a fruit or vegetable. Just go a food store and see all the tasty, calorie-rich food presented before you–desserts, slow-cooked meats, breads, donuts, candy, etc.–is it any wonder people are gaining weight? Could it be any more obvious? Just as “It’s the economy, stupid” , it’s the food, stupid. Same for excess snacking. Just 2-3 high-calorie snacks is equal to a single meal.

A single chewy Chips Ahoy! Reese’s peanut butter cup cookie, which is about the size of a Kennedy half-dollar coin, packs 80 calories. It would be easy to eat the package, about 1400 calories, in a single sitting while mindlessly surfing the web, watching TV, or playing video games. The cookies dissolve in your mouth; no conscious effort like chewing, that would require at least being mindful of the presence of food, is even needed. The extreme caloric density, palatability, and softness, makes modern food better suited for burn victims, or people with cancer or Chron’s disease, not healthy, able-bodied people. It’s not so much that modern food is making Americans sick, but that we’re eating the type of food intended for people who are too sick to eat normal food. Hence, too many calories and obesity as a result.

Age also plays a major role, in that people tend to gain weight with age, especially past 30. Some people gain only a little weight but others gain a lot, even without much of a difference of food consumption or lifestyle change over the intervening decade. Some people just seem to ‘blow up’, and no one really knows why. Pick any celebrity and most are heavier now than they were in their 20s, and this is despite having a lot of money, access to top personal trainers, and expensive diets and chefs. Famous examples of this sudden ballooning weight phenomenon are Elvis Presley and Marlon Brando. Or John Travolta…rail-thin in the ’70s and ’80s and then–boom–put on weight in the ’90s.

This even is observed going back 100s of years, such as paintings of the Founding Fathers, in which at least half of them appear at least overweight, similar to ratios seen even today, such as Benjamin Franklin and John Adams. And this was centuries before the advent of processed foods, GMOs, super-sized fast food portions, etc. I think this further lends credence to the underdiagnosed obesity hypothesis. More research needs to be done in understanding why things go haywire at 30 and treating it. I don’t think there is much urgency in the health community to do anything. It’s basically accepted as an inevitability that people will gain weight with age.

Related to obesity being underdiagnosed, pharma companies were not making enough money with diabetes drugs, so the category of pre-diabetes was created even if it does not have symptoms, does not lead to diabetes, or meet the strict criteria of being a pathology. Similar to obesity, cholesterol became such a big deal over the past 30 years, not because Americans suddenly had worsening cholesterol levels, but doctors and marketers became aware of it, which led to many people being diagnosed with high cholesterol and the development popular drugs like Lipitor, in 1997, to treat it. Same for endless other blood markers, which are of mixed to no predictive significance. There is no consensus about cholesterol, good vs. bad fats, lipids, etc. Having high cholesterol or high blood pressure does not mean the development of disease. Even if it’s a risk factor, that is part of my point: more identifiable risk factors means more drugs.


  1. The problem still is too much sugar also. I think by the time of the founding Fathers sugar plantations were in full production. And being upper class the founding Fathers had access to too much added sugar.

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