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Ask An Economist

Friday, October 1, 2010
Adrian Peralta-Alva has been an economist in the Research division of the Federal Reserve Bank of St. Louis since May 2008. His expertise is macro-economics. Recently, he has been studying whether it is a good idea to spend more on infrastructure as a way to boost the economy now that housing construction has slowed down so much. In his free time, he enjoys spending time with his family, traveling and playing outdoor sports.

Why have Americans gained so much weight during the past 50 years?

The average weight of an American adult female has increased by 14 pounds since the early 1960s, going from 140 to 154 pounds. The average weight of an adult male has increased by 16 pounds, from 166 to 182. Obesity rates have risen dramatically as well. What is behind this increase in weights? The quick answer is lower taxes, along with higher wages for women.

The consensus in the medical literature is that people gain weight when calories consumed are greater than calories expended. A switch to sedentary lifestyles in the U.S. is an important factor accounting for obesity levels. However, the switch to a sedentary lifestyle in the U.S. occurred before the mid-1960s. Further, estimates of the decline in calories expended in the U.S. suggest these changes are too small to account for recent increases in weights. It is well-established, nevertheless, that American adults consume more calories now than in the 1960s.

Hence, Americans have gained weight because they consume more calories than before. But why has this occurred? Nationally representative data of food consumption by U.S. individuals suggests that this increase in caloric intake can be attributed to a dramatic increase in calories consumed from food prepared away from home (restaurants, fast food, snacks, frozen pizza eaten at home, etc.), which more than compensated for a simultaneous decline in calories consumed from foods prepared at home from scratch.

Economic theory can help us understand the changes in the food consumption patterns of American households. In fact, these changes roughly coincide with important declines in income taxes and with a substantial increase in the average wage of women relative to that of men. Both of these changes increase the opportunity cost of cooking at home from scratch. A higher opportunity cost of time can also help us understand some of the dramatic changes in time use patterns of American households during the last 50 years. Married females devote more than twice the number of hours to jobs outside the home while the total household time devoted to food preparation and cooking has gone down by a factor of two. Since high consumption of food prepared away from home may be here to stay, policies focused on informing individuals so they can make healthier choices when eating food prepared away from home may be useful in controlling the obesity epidemic. If consumers demand healthier food, then the establishments that produce it may respond by providing higher quality food, achieving a virtuous cycle as well.