Tomas
Philipson and Darius Lakdawalla
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.
