Although the involvement of genes in weight and body shape is obvious, they cannot explain the recent increase in obesity rates.

In the last few decades, genes have not changed but the environment surely has. There are five leading environmental culprit causing the worldwide weight-gain epidemic.

  1. the increased abundance of inexpensive, diverse, high-fat foods
  2. the tendency to eat high-calorie food on the go rather than unhurried meals
  3. the increase in energy-saving technology, such as remote controls
  4. the speed and convenience of driving rather than walking or biking
  5. the preference for watching television and videos rather than exercising

Most human beings are predisposed to gain weight when rich food is abundant because, in the past, starvation was all too often a real possibility. Therefore, a tendency to score calories in the form of fat provided a definite survival advantage. We have no counter-mechanism to prevent our bodies from gaining too much weight when all those yummy foods are so available as they are now. When diets are more or less routine and predictable, people habituate to what they are eating and eat less of it. As food become more varied people eat more and gain more weight. In addition, in America, portion sizes have become “gargantuan” according to many Europeans and Asians.

Exercise is another nongenetic influence on weight. Exercise boosts the body’s metabolic rate and may lower its set point. When obese women are put on a severely restricted diet their metabolic rates drop sharply. But when they combine the diet with moderate physical activity, such as daily walking, they lose weight and their metabolic rates rise. This is true even for those who are genetically susceptible to obesity.

Cultural customs and standards of what the ideal body should look like shape eating habits and activity levels. In many places around the world, especially where famine and crop failures are common, fat is taken as a sign of health, affluence in men, and sexual desirability in women. In the United States, African-Americans and Mexican-Americans are much more accepting of fat people than white Americans.

The ironic thing is that despite the overall rise in weights the cultural ideal for white women in the United States, Canada, and Europe has been getting thinner and thinner. Today the female ideal is an odd combination of big breasts and no hips. Pressures for American men to be “buff” and strong have also increased.

Inexpensive food and a lack of exercise are doubtless factors in weight gain, and it looks as though individual's genetics may be in mix too. Then again, maybe people get fat for the simplest of all reasons: because they can - that is, because they're programmed by evolution to pork up to survive famines. Maybe. But some other causes could be added to the above, which might possibly be even more important:

Decreased nutritional density of food

Studies now say that food raised in the 1950s had twice the nutritional value, that is twice as many vitamins, minerals, etc., per pound as food raised today by more efficient industrial methods from seed that has been bred to grow fast and not bred to be nutritionally dense. If you have to to eat twice as much to get essential nutrients, you'll probably do just that. Maybe it's time to go organic to help lose those pounds. More nuts and seeds anyone? (I recommend nuts because it takes a long time to grow a generation of trees, making it far harder for the food industry to modify their genetics enough to breed the goodness out of them - but they're working on it.)

Microwave ovens eliminating nutrients

A study reported in the 25 October 2003 issue of New Scientist magazine, p14, found that microwave ovens remove something like 95% of important antioxidants and flavonoids. It's thought that the extreme heat created by the microwaves could be the culprit, and that by dialing down the power level to 10 or 20 percent, this may be avoidable. (The same study found that boiling is better, and steaming best.) As above, if you have to eat much more food to get the same amount of essential nutrients, you probably will. Maybe it's time to get back to the stove.

Disappearance of food smells from the environment

Recent studies show an intimate and somewhat paradoxical tie between food smells and appetite. It would seem that being around food smells tends to make us less gluttonous over time - it's been hypothesized that we (unconsciously) interpret the relative absence of food smells in the environment as a sign of famine or impending famine, and begin to pork up. Subjects have been helped to lose weight by handing them scent tubes for chocolate or other foods and instructing them to smell them regularly throughout the day. But there's another side to this. We're all inundated with artificially strong pine scents, laundry scents, air fresheners, scented toothpaste, mouthwash, and underarm deodorant, ozone, scents from electrical equipment, cleaning solvents, plastics, and much more, all of which put together are loud "noise" through which subtle environmental food scents aren't that likely to penetrate. Lose the ammonia cleaners, and maybe we'll smell the food and lose the love handles, too?

Anxiety from broken social networks/lack of community/noise/crowding/frequent encounters with strangers

Anxiety can cause increased calorie intake, perhaps as an unconscious precautionary measure, and this modern world just isn't the social or physical environment we evolved in. No hunter-gatherer met a few hundred people he or she had never seen before on the way to or from work... unless maybe it was their last day on earth.

Exposure to sucrose and refined carbohydrates.

All of these are absorbed into the bloodstream as sugar much more quickly than sugars found in nature such as fructose (fruit sugar). They either don't suppress appetite as well, or for nearly as long, or both. Studies show eating sugar (sucrose) before a meal actually increases appetite.
The (controversial) advent of High Fructose Corn Syrup as as a widespread sucrose substitute may have redressed this somewhat, but of course, nutrients, vitamins and fiber are not provided along with the sugars, as would be the case if you ate some fruit. Note that mirror forms of sugar, such as liquid invert sugar are especially unnatural and may not be healthy either. First posted: Sat Feb 21 2004 at 9:20:50 Last revision: Thu Mar 11 2004

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