People discuss obesity as an epidemic, but the solution somehow remains individual action. That doesn’t work for real epidemics. You can’t, for instance, not catch smallpox all by yourself. (You can be lucky and have natural resistance, but that’s different.)

It’s turning out that people spoke more truth than they realized. Evidence is accumulating that obesity is a real epidemic, i.e. a public health issue with social and environmental causes. It’s something I’ve suspected for years.

Obesity has become more prevalent over the last thirty to forty years. That means — at the population level — it can’t be caused by the human tendency to eat too much. People have always been primed to eat too much, but large numbers of very overweight people relative to the whole population is a phenomenon of the last few decades.

And note that this isn’t just a matter of changing measurements or statistics. When coffin makers have to upsize coffins because the ones they’ve used for decades no longer work, there’s a real change. It’s not just PR.

So the cause(s) of the problem have to be something that’s changed in the last few decades. I’ll list all the changed factors I can think of, but the one I want to talk about is the last. Some of them are most developed in the US, but if and when they manifest elsewhere, they can be expected to promote obesity likewise.

• The baby boom generation, which is large relative to the whole population, has aged, and older people are often heavier. (A factor beyond anyone’s control.)
• Advertising for high-calorie fast food has grown very sophisticated and ubiquitous, and fast food is much more available. (A social environment factor that requires changes to industries.) (A side note: advertising is not something that can be simply ignored. It functions to steer choices whether you’re paying attention or not. The only way to avoid its effect is to avoid the advertising itself, which involves avoiding almost all modern media. Individuals may do that, but it’s not going to happen at a population level, and that’s where public health issues operate.)
• Related to that is the increase in drinking sweetened sodas. That’s upped average calorie intake by a couple of hundred calories per day. (Again, advertising and availability combine to make this a social environment factor.)
• Related to both of the above is the use of refined sugar, which has never before been used on the huge scale of the last few decades. It promotes obesity by the simple mechanism of making it too easy to get too many calories. There’s also a potential added wrinkle involving high fructose sweeteners. Scientists argue about its effect. Fructose is processed differently than glucose, and given the way it’s regulated, it could be a contributing factor to the problem. (A social environment factor due to industry practices and agricultural subsidies.)
• Urban factors contribute as well. Urban sprawl makes distances too big for walking. Use of mass transit, which requires walking to and from stops, has declined versus personal cars. And many urban areas don’t have adequate parks or play spaces where adults and children can be physically active. Epidemiology indicates that (lack of) urban planning is a measurable factor in increasing obesity. (NYTimes 2003 article) (Another social environment issue.)
• Last, there’s my pet peeve: endocrine disruptors. These are pollutants that are byproducts of some plastics, some agricultural chemicals, some hormone therapies, and the like. Bisphenol A (BPA) is a well known example. Once they’re in the environment they can break down into related compounds, they get into the food chain, and once they’re ingested, they latch on to some of the same receptors as the body’s own hormones. Once they’ve latched on, they can rev up or shut down the normal function, or they can cause strange results not in the body’s normal repertoire. Widespread endocrine disruptor pollution has happened only in the last few decades. (An environmental factor involving dozens of industries.)

Recent research (press release, article summary in Cell Metabolism) has shown that estrogen receptors in the brains of female mice regulate hunger and energy expenditure. (Male brains likewise have various androgen and estrogen receptors and are expected to have similar regulatory pathways. However, that wasn’t the topic of this research. The recent increase in the phenomenon of “man-boobs” on young and not-obese men shows rather plainly that endocrine disruptors have no less effect on fat deposition in men.)

Interestingly, one implication the researchers draw is that estrogen replacement therapy for postmenopausal women may have an overlooked benefit by keeping weight down and therefore keeping the complications of obesity down.

However, they don’t draw the far more significant implication for the entire population. If sex hormone receptors regulate energy balance, and if we’ve flooded the environment with bad substitutes for sex hormones, is it any wonder that people are having trouble regulating energy balance?

It’s one more instance where the flood of chemicals released by modern industry is affecting the environment, in this case the environment of the human body.

Like all public health issues, nothing less than a population-level approach will work. Dysentery, cholera, and typhoid are never wiped out by drinking boiled water. They’re wiped out by building municipal sewers. Smallpox wasn’t eradicated by avoiding smallpox patients. It was eradicated by universal vaccination. The individual actions aren’t useless. They just don’t change the widespread causes of the widespread problem.

Modern health problems like cancer and obesity aren’t going to be wiped out by eating fresh vegetables. Eating veggies is good, but it doesn’t address the basic problem. That’s going to take nothing less than a change to clean sustainable industry.

It’s almost enough to make you wish a mere diet really was all that’s needed.