In a recent 35-page report, two economists attempted to explain why we're all getting fatter. First, relative to consumer goods as a whole, the price of a calorie has dropped by 36 percent since 1977.

And, naturally, we tend to eat more as food prices decline. There's another factor at work, however, because although food prices leveled off in the mid-1990s, we have continued to gain weight. And that factor is an upward adjustment in what we consider to be appropriate body weight. When we compare ourselves to everyone around us, we think we look just fine.

The two economists, Mary Burke and Frank Heiland, studied the weights of woman between thirty and sixty years old from 1976 to 2000. During that period, the women's average weight increased by twenty unwelcome pounds.

In 1994, an average woman weighed 147 pounds but wanted to weigh only 132 pounds. By 2002, she weighed 153 pounds and wanted to weigh 135 pounds. The numbers indicate that, in spite of recurring controversy over anorexic movie stars, there is less social pressure to be thin.

The fatter we get, the more our body image standards relax, and that process, so to speak, just feeds on itself. The finding is corroborated by an earlier study, which indicated that 87 percent of Americans, including 48 percent of the obese, think that their body weight falls in the "socially acceptable" range.

Source: EurekAlert; Social Dynamics of Obesity by Burke and Heiland