 Reducing the prevalence of obesity in the population is one of the Healthy People 2010 goals. Increased vigilance is required in all age groups in preventing and reversing overweight and obesity. On an individual level, behavioral factors that influence body weight include eating choices leading to excess calorie intake and physical activity patterns leading to diminished calorie expenditure. An imbalance between the two over time leads to increased weight. On a population basis, the prevalence of overweight is associated with a myriad of influences, including social, behavioral, cultural, and environmental factors as well as genetic and physiological factors. For a majority of overweight individuals, restoring a balance between energy intake and expenditure is difficult, and therefore there is an increasing emphasis on preventing obesity on a population level. The long-term goal of this research is to prevent further increase in rates of obesity in the population. In the adult population of working age, a majority of the day is spent in the worksite, suggesting that interventions at the worksite level may offer the opportunity for success in this age group. It is anticipated that this project will yield important contributions to the understanding of obesity prevention. 