<http://www.uni-kiel.de/ifw/konfer/newtech/loureironayga.pdf>
There are mainly two arguments that could justify the growth of overweight problems around the world: some researchers argue that obesity growth is mainly due to a higher intake of calories, while others state that obesity is mainly caused by a lower expenditure of calories in daily activities. In line with the calorie consumption argument, Cutler, Glaeser, and Shapiro stated that Americans have become more obese over the past 25 years primarily due to the consumption of more calories. Analyzing changes in food consumption between the mid-1970s and the mid-1990s for male and females, they showed that the growth in caloric consumption is enough to explain the increase in weight. However, they pointed out that the main reason for increased dietary caloric intake in the U.S. was calories consumed outside of the main meals (i.e., snacks). They showed that Americans nowadays eat more frequently than they used to, even though average caloric consumption at dinnertime has been somewhat reduced. Their results also suggested that obesity is not primarily the result of more women working in the labor force.
Other recent obesity related studies by economists are those by Philipson and Posner, Philipson, and Lakdawalla and Philipson. They all concluded that increases in BMI over time are related to a lower use of calories (due to reductions in the strenuousness of work). Philipson and Posner presented a theoretical model that suggests that technological change is a major factor that contributes to rising obesity rates. Philipson also suggested other potential reasons that could explain the growth of obesity rates. These reasons include, among others, the change from rural to urban societies and changes in cultural habits, such as a higher rate of passive entertainment. Lakdawalla and Philipson, on the other hand, used data from the National Health Interview Survey from 1976 to 1994, and from the National Longitudinal Survey of Youth from the period 1982 through 1998. They empirically estimated the relationship between obesity and reduction of physical activity and concluded that about 40 percent of the total growth in obesity is due to expansion of the food supply, potentially through agricultural innovation, and about 60 percent is due to demand factors such as decline in physical activity in market and home production.
Chou, Grossman and Saffer looked at the role played by other societal forces that may alter the individual's time allocation for food preparation and consumption in an industrialized society. In particular, their main hypothesis was that given the higher value of time in industrialized societies, individuals would devote more time to the labor market, thereby having less time available for food preparation and leisure. Using cross sectional data from the Behavioral Risk Factor Surveillance System (BRFSS), they analyzed, among other factors, the role of the different restaurants, the price of a meal in each type of restaurant, the price of food consumed at home, the price of cigarettes, hours of work per week and hourly wage rates by socio-demographic characteristics. Their main results indicated a large positive effect associated with the per capita number of restaurants. In addition, the authors found that downward trends in food prices account for part of the upward trend in weight related incidence, while increases in cigarette prices are associated with growth in weight related problems.
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Direct interpretation of the coefficients allows us to assess the relative impact of each of the explanatory variables, ceteris paribus. Based on the results obtained via GLS models with random effects, an extra 100 calories in the daily calorie intake correspond to an average growth of 0.6 percent in the number of individuals with overweight problems and an average growth of 0.8 percent in the number of obese individuals, ceteris paribus. Further, an increment of 1 percent in female labor force participation rate increases the number of overweight individuals by 0.52 percent, while female labor participation is not a statistically significant factor contributing to obesity. Mitigating factors such as expenditures in education and contributions from consumers to the agricultural sector (via agricultural prices) seem to have a higher impact on reducing exclusively obesity problems than on reducing the incidence of general overweight problems. A 1 percent increase in the percentage of CSE [= consumer support estimate, a proxy for protectionist ag subsidies] contributions decreases the percentage of individuals with general weight problems (overweight and obese) by 0.06 percent and the number of obese individuals by 0.12 percent. In terms of expenditures in education, a 1 percent increase in GDP dedicated to education decreases the incidence of obesity by 2.41 percent, while it is not a statistically significant mitigating factor in the case of general overweight problems. The importance of the effects of change from rural to urban societies and the reduction of physical activity on overweight and obesity rates are reflected by the magnitudes of the parameter estimates of the variables denoting the percentage of rural population and the number of kilometers driven by cars. Specifically, a 1 percent increment of rural population decreases the general overweight rate by 0.40 percent, while an additional thousand of kilometers per capita driven by private cars increases on average the obesity rate by 0.46 percent, ceteris paribus.