Americans, like most people in the industrialized world, are getting heavier. That much is clear.

But the reasons why our waistlines are expanding so fast are still a bit murky.

Sure, there is a simple explanation: we eat too much, and don’t get enough exercise. But that explanation doesn’t really get at the heart of the matter. It’s not as if we all sat down one day and decided to loaf around and eat bon bons and potato chips. Culturally, thin is still in; and most of us who are packing on a few extra pounds would prefer to take it off, if we could.

A more plausible explanation is that, in a host of subtle ways, our physical and cultural environments have gradually changed, transforming sloth and gluttony from deadly sins into convenient choices.

Of course, some researchers posit that we worry too much about diet and exercise, and not enough on other, often overlooked causes of weight gain. A recent article in the International Journal of Obesity, for example, cites a variety of unheralded factors that collectively contribute to growing waistlines, ranging from declining rates of smoking (nicotine is an appetite suppressant), to too little sleep (staying awake stimulates the appetite), to new medications (some antidepressants are linked with weight gain), to climate-controlled environments that require our bodies to expend less energy on heating and cooling.

Still, there’s plenty of evidence that cheaper food has made it much easier to overeat. American agriculture has seen a startling increase in productivity over the last several decades. According to the USDA’s Economic Research Service, per-capita calorie availability grew from 3,200 calories per day in 1980 (about where it had been for a generation) to 3,900 calories per day today. That means that we eat (or waste) about 700 extra food calories per day than we did in 1980.

  • Looking at this graph, it’s easy to believe that the rising production of food (and the consequent fall in the price of a calorie) must have been a big factor in the rise in obesity; American’s weight rose roughly in tandem with food overproduction.

    But then there’s a dilemma: do we really want calories to get more expensive? My budget could probably handle it if food got more expensive, but certainly not everyone’s could.

    Then again, much of the reason that food is so cheap is that many foods—particularly grains, like corn and wheat—are so heavily subsidized. End the subsidies, and perhaps we’d produce a little less corn, soybeans, wheat, and rice; the cost of an empty calorie would rise; and high-calorie eating would take a bigger bite out of our wallets. And if we were really clever, the money we saved on farm subsidies could be put back into nutrition programs, such as school meals and food stamps (which also benefit farmers by stimulating demand). Net result—food’s a little more expensive, people eat a little more healthfully, and lower income folks can still afford a healthy diet.

    A fellow can dream, can’t he?