Harris School professor takes on some weighty topics
>>Tomas Philipson argues that though obesity may be a medical problem, it represents an efficient economic outcome.

A former member of the Swedish national volleyball team, Tomas Philipson knows something about fitness. And as a graduate of the University of Pennsylvania's Ph.D. program in economics, he can play the numbers game as well.

Former volleyball player Tomas Philipson blames obesity on economoics not french fries.

Since 1998, he has combined these enthusiasms as a professor in the Irving B. Harris Graduate School of Public Policy Studies, scoring points by applying economics to health-related topics, such as elderly care, AIDS, and life expectancy. "Like most scholars," he says, "I want to work on topics that are important and that haven't been studied--particularly when people don't think they have anything to do with economics."

His latest example is a working paper, co-authored by Law School senior lecturer Richard A. Posner, that links technological advances to a worldwide rise in obesity. The paper--to be submitted soon to a professional journal--grew out of the authors' surprise that more had not been written on the economics of obesity, given the condition's prevalence and costs. The World Health Organization recently declared obesity an international "epidemic," common in industrialized nations and on the rise in developing countries. Meanwhile, the U.S. Department of Health and Human Services estimates obesity cost the nation $99 billion in medical expenses and lost productivity in 1995 alone.

In "The Long-Run Growth in Obesity as a Function of Technological Change," published as a working paper by both the Harris School and the National Bureau of Economic Research, Philipson and Posner argue that economic incentives are behind the poundage surge that has left 10 to 25 percent of adults in Western countries medically overweight. They don't dispute that the expansion of the world's waistlines stems from taking in more calories than are burned through physical activity. But they do hope their paper will help turn conversation about the upward trend from its current emphasis on changes in how people eat to a discussion of changes in how they work.

Obesity boils down to economics, Philipson says, for three main reasons. First, economically spurred technological advances in food production and distribution have made high-calorie, fast-food diets possible. Second, those same advances have made the overall economy increasingly more dependent on bytes than brawn. Moreover, individuals get fat only after weighing the economic costs and benefits of calorie consumption against their personal preferences. "The price of taking in more calories has gone down and the price of spending them has gone up," he explains. "To get paid in the past you had to engage in manual labor. Now it's the opposite. You have to pay with your time to exercise off the job."

To portray obesity in economic rather than health terms, Philipson and Posner designed mathematical models to account for the interplay of such factors as weight, diet, labor supply, and off-the-job exercise. "Math allows you to be more precise in your thinking and disciplines what you are thinking," Philipson says. "Initially, it's my primary tool. You learn about a problem by setting up a world where the problem exists and then seeing what in that world will affect it. The key is understanding that theoretical and empirical work are complementary."

In their mathematically modeled world, the researchers found that the rise in obesity can be viewed as an efficient outcome of economic and personal decisions. Generally speaking, Philipson says, "people would rather take higher-paying jobs and be obese than take lower-paying, more physical jobs and be thin. If people could choose to be their medically recommended weight without consequences, then they might want to be that. But it isn't without consequences. It has an economic-opportunity cost."

However, note the researchers, individuals in technologically advanced countries are not likely to balloon unchecked. Modeling the relationship between income and weight, they show how obesity tends to fall as income rises in rich countries and rise as income rises in poor countries. When food prices are low, Philipson explains, people spend a smaller share of their income on food and tend to consume more calories, but only up to a certain point--at which concerns for being above their ideal weight kick in. By contrast, in poorer, less developed countries where food prices are high, obesity becomes a physical symbol of wealth.

Considering obesity as self-limiting and as primarily resulting from technology rather than health-related reasons, such as increases in calorie consumption or declines in cigarette smoking, Philipson and Posner conclude that government-funded public education initiatives will not effectively ward off fat. Take for example, Philipson says, the U.S. Department of Health and Human Services' Healthy People 2010 campaign, which aims in part to reduce obesity. Its Web site (www.health.gov/healthypeople) warns that obesity substantially raises the risk of a host of illnesses, including Type 2 diabetes, heart disease and stroke, gallbladder disease, arthritis, and certain cancers, and recommends that obese people significantly change their eating, shopping, exercising, and social habits.

The problem, says Philipson, is that the right incentives are not in place. "It doesn't take a rocket scientist to know how to lose weight," he says. "Most people know there are adverse consequences to being overweight. Knowing the exact details of their risks probably won't change their behavior because they've already taken the risks into account and accepted the tradeoffs on an individual level." Instead, Philipson suggests, if the government really wanted to influence people's weight, it would provide subsidies for physical activity or tax calorie intake. "What will change behavior," he says, "is a change in the incentives."

Philipson plans to continue studying how technology has contributed to obesity. He'll be comparing how technological advances have affected the weight of workers in different occupations and trying to answer questions such as whether blue-collar workers tend to put on pounds when they retire while white-collar workers shed them.

Although his research provides a different rush than that of a professional volleyball player--a path Philipson says he might have pursued were it not for a knee injury in his early 20s--he has enjoyed the similarly competitive nature of scholarship. "Academics come up with new ideas that help to better explain facts," he notes, "so in a sense academics come up with ideas that out-compete old ones." --C.S.