Adult body mass index trajectories and sexual orientation: the Nurses' Health Study II.

BACKGROUND:Cross-sectional research has documented elevated prevalence of obesity in lesbian and bisexual women relative to heterosexual women, but little is known about disparities in longitudinal patterns in BMI change during adulthood. PURPOSE:To examine sexual orientation-related disparities in individual BMI trajectories throughout adulthood. METHODS:Data on BMI, sexual orientation, and sociodemographics were gathered prospectively from 1989 through 2005 from 90,713 U.S. women in the Nurses' Health Study II and examined in 2011 using general growth mixture modeling to identify BMI trajectories from ages 25 to 59 years. Multinomial logistic regression was used to determine whether sexual orientation was associated with BMI trajectory group membership. RESULTS:Four BMI trajectory groups were identified and labeled based on mean BMI within each group at baseline and final follow-up: Group 1: slow-weight-gain trajectory; Group 2: moderate-weight-gain trajectory; Group 3: rapid-weight-gain trajectory; and Group 4: obese-to-overweight trajectory. Lesbian and bisexual women showed consistently higher odds of membership in Groups 2-4 (adverse-weight-gain trajectories) versus Group 1 (the slow-weight-gain trajectory) relative to heterosexual women. CONCLUSIONS:Both lesbian and bisexual women were more likely than heterosexual women to experience adverse-weight-gain trajectories in adulthood. New research efforts are needed to understand and eliminate these pronounced disparities.