Gender Expression Associated With BMI in a Prospective Cohort Study of U.S. Adolescents

OBJECTIVE: To examine the relationship between gender expression (GE) and BMI in adolescence. METHODS: Repeated measures of weight-related behaviors and BMI were collected 1996-2011 via annual/biennial self-report surveys from youth ages 10 to 23 years (6,693 females, 2,978 males) in the longitudinal Growing Up Today Study. GE (very conforming [referent], mostly conforming, nonconforming) was assessed in 2010/11. Sex-stratified, multivariable linear models estimated GE group differences in BMI and the contribution of sexual orientation and weight-related exposures to group differences. Models for males included interaction terms for GE with age. RESULTS: In females, mostly conforming youth had 0.53 kg/m(2) and nonconforming had 1.23 kg/m(2) higher BMI; when adding adjustment for sexual orientation and weight-related exposures, GE-group estimates were attenuated up to 8% and remained statistically significant. In males, mostly conforming youth had −0.67 kg/m(2) and nonconforming had −1.99 kg/m(2) lower BMI (age [in years] interactions were between −0.09 to −0.14 kg/m(2); when adding adjustment for sexual orientation and weight-related exposures, GE-group estimates were attenuated up to 11% and remained statistically significant. CONCLUSIONS: GE is a strong independent predictor of BMI in adolescence. Obesity prevention and treatment interventions with youth must address ways that gender norms may reinforce or undermine healthful behaviors.