This paper examines human obesity, measured as weight and body mass index (BMI), and its determinants in Russia. Obesity increased dramatically during transition from a planned to a market economy, by 38%. We determine the factors contributing to rising obesity using individual level data from the Russia Longitudinal Monitoring Survey for 1994 and 2004. We find a strong positive effect of diet/caloric intake and a strong negative effect of smoking on weight and BMI. Gender, education, and income are other major determinants of obesity. Our analysis provides information on dietary patterns and other determinants of obesity in Russia which is essential for formulation and implementation of effective policies designed to reduce the problem and improve the health of the population.