Effects of Less Demanding Work and Greater Food Supply on Weight

Public health officials have long warned of the alarming rise in obesity among Americans. With close to half the U.S. population carrying too much weight, and with more Americans obese than those who smoke, use illegal drugs, or suffer from ailments unrelated to obesity, the country has reason for alarm.

Weight gain is not a recent phenomenon, however. Over the last century, a six-foot man has gained about 30 pounds (as measured by body mass index, or BMI). Surprisingly, however, this weight gain has occurred even as calorie consumption has declined. Indeed, the immediate postwar period saw substantial growth in weight amid declining calorie consumption. Nor has
demand for food increased. Calorie consumption has declined even amid steadily declining food costs.

Any analysis of weight, therefore, must move beyond a focus solely on food consumption. As Darius Lakdawalla and Tomas Philipson find in their working paper, “The Growth of Obesity and Technological Change,” technological advances and their effect on work and food availability combined are key to weight gain.

Technological advances have moved society from an agriculture-based economy at the turn of the century, through industrialization, and most recently, into a service- and information-based economy. In an agricultural or industrial society, work is strenuous and food is expensive. In effect, the worker is paid to exercise. He must also forgo a larger share of his income to replace the calories spent on the job.

In a post-industrial society, in contrast, a smaller share of one’s income is needed to replace the calories one expends. In addition, individuals must, in essence, pay for exercise given that they now have to devote their leisure time to getting the exercise they once got at work. Therefore, work is less strenuous, exercise more costly, and food less expensive. The result: weight gain.

The important point is that neither less demanding work nor greater food supply alone can account for the weight gain. Rather, the two combine to affect weight, albeit not evenly. Less strenuous work contributes slightly more to weight gain than expanded food options. About 40% of the growth in weight is due to the expansion in the food supply, and 60% to less strenuous work and more sedentary lifestyles.

Policy Implications

Currently, the major public interventions against obesity involve education programs that emphasize the benefits of good diet and exercise. However, if technological change in production is the major factor driving weight gain, education and information may be less effective than incentives. Further, given that work is no longer a central source of exercise, more attention should be paid to leisure time as a source of exercise. Especially for children, the technological advances of computers and television have lowered the calories expended
in leisure time, which may be contributing to the rise in child obesity.

Data

The authors use three data sets: the National Longitudinal Study of Youth (NLSY) from 1982–1998, the National Health Interview Survey (NHIS), and the National Health and Nutrition Examination Survey (NHANES), from 1988–1994. To measure job strenuousness, they use the Dictionary of Occupational Titles, 4th edition, which contains various ratings of the strenuousness of occupations.

Tomas Philipson is a professor in the Irving B. Harris Graduate School of Public Policy Studies and a faculty member in the Department of Economics and the Law School at the University of Chicago. Darius Lakdawalla is an associate economist at the RAND Corporation. This working paper is also available through the National Bureau of Economic Research Working Paper Series.