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 from 1996 to 2011 via annual/biennial self-report surveys from youth aged 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 and -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.