DESCRIPTION (provided by applicant: Sexual Orientation and Obesity: Test of a Gendered Biopsychosocial Model Obesity is one of the most critical public health issues affecting the U.S. today. Racial and socioeconomic disparities in the determinants, distribution, and consequences of obesity are receiving increasing attention; however, one area that is only beginning to be recognized is the striking interplay of gender and sexual orientation in obesity disparities. It is now well-established that women of minority sexual orientation are disproportionately affected by the obesity epidemic, with nearly three-quarters of adult lesbians overweight or obese, compared to half of heterosexual women. In stark contrast, among men, heterosexual males have nearly double the risk of obesity compared to gay males. Despite clear evidence from descriptive epidemiologic research that sexual orientation and gender markedly pattern obesity disparities, there is almost no prospective, analytic epidemiologic research into the causes of these disparities. It will be impossible to develop evidence-based preventive interventions unless we first answer basic questions about causal pathways, as we plan to do. Our study has high potential for public health impact not only for sexual minorities but also for heterosexuals, as we seek to uncover how processes of gender socialization may exacerbate obesity risk in both sexual minority females and heterosexual males. In response to PA-07-409 Health Research with Diverse Populations, we will rigorously test our innovative gendered biopsychosocial model that is both multilevel and multisystem to explain observed sexual orientation disparities in obesity. We will use longitudinal, repeated measures survey data and also biological data from three youth cohorts: Growing Up Today Study (GUTS) 1 & 2 and National Longitudinal Study of Adolescent Health (Add Health), all ongoing prospective cohorts that together total over 47,000 youth living throughout the United States.