This will be a large-scale, prospective, longitudinal, clinical study using an epidemiological approach. The 1200, free-living participants age 20-35 will be equally divided by gender and race (Caucasian and African-American). Among the participants, 1/3 will have no obese parent, 1/3 will have one obese parent, and 1/3 will have two obese (body mass index, BMI > 30 kg/m2) parents. The participants will undergo a series of assessments in the domains of diet, physiological factors, and behavioral factors at baseline and every 12 months thereafter (unless otherwise noted in Approach and Research Procedures) for 10 years.