Obesity and Physical Fitness in the Labor Market

Mixed results have been reported when body size is used to estimate the effect of health and nutritional status on worker productivity. This dissertation offers an alternative hypothesis that body composition rather than body size is responsible for the effects of health and nutritional status on worker productivity. Body fat is responsible for the poor health associated with obesity. Lean body mass is responsible for the superior performance associated with physical fitness. Studies using body size alone cannot distinguish the combined, but opposite effects, of body fat and lean body mass. A method is provided here that overcomes the lack of data for body composition. The clinical information available in the Third National Health and Nutrition Examination Survey 1988-94 (NHANES III) is used to estimate body composition for the survey participants in the National Longitudinal Survey of Youth (NLSY 1979). The inclusion of estimated body composition in the estimated wage equation shows that the effect of lean body mass on the wage rate is positive while the effect of body fat is negative. Estimated body composition is then used to examine the role of physical differences in the gender wage gap. The decomposition of the gender wage gap shows that most of the previously unexplained differences in wages between men and women can be attributed to the gender differences in body composition. The explanatory power of estimated body composition rises significantly with occupational physical strength requirements. This result suggests that estimated body composition is capturing occupational requirements previously omitted from the past studies. The findings presented in this dissertation indicate that body composition plays an important, though previously unidentified, role on wage determination. It is clear that capital investments in body composition yield economic dividends by impacting hourly wages of workers. Empirical studies that do not address differences in body composition risk obtaining biased results. Future public health policies should take into consideration the combined but opposite effects of body fat and lean body mass. It is not body size alone, but the compositional makeup of the human body, that public health policies may need to address