Associations of body mass index with sexual risk-taking and injection drug use among US high school students

The purpose of this study was to determine if overweight and obesity function as indicators of increased risk for HIV and other sexually transmitted diseases (STD) among US high school students. We analyzed nationally representative data from the national Youth Risk Behavior Surveillance System to examine associations of body mass index (BMI) with sexual risk-taking and injection drug use among sexually active high school students, using sex-stratified logistic regression models. We also examined possible mediators of these associations, including suicidal thoughts, early sexual initiation, sexual violence, and use of alcohol and drugs before sex. Controlling for race/ethnicity and grade, among female and male students, both underweight (BMI<5th percentile) and obesity (BMI≥95th percentile) were associated with decreased odds of being sexually active (i.e., having had sexual intercourse in the past 3 months). However, among sexually active female students, obese females were more likely than normal weight females to have had ≥4 sex partners (odds ratio, OR=1.59), not used a condom at last sexual intercourse (OR=1.30), and injected illegal drugs (OR=1.98). Among sexually active male students, overweight (85th percentile≥BMI<95th percentile) was associated with not using a condom at last sexual intercourse (OR=1.19) and obesity was associated with injection drug use (OR=1.42). The inclusion of suicidal thoughts and early sexual initiation in models reduced the strength of associations between obesity and sexual risk-taking and injection drug use among sexually active female and male students. Among sexually active students, overweight and obesity are indicators of increased risk for HIV and other STDs.