Examining Adolescent Substance Use and Obesity Among a Nationally Representative Sample

Background:  Obesity rates among children and adolescents in the United States have tripled in the last 30 years.  Current studies are inconclusive about the relationship between adolescent obesity and substance use.   Girls and boys and racial/ethnic minorities have different patterns of obesity, and this paper examines the gender and race moderator effects on the association between adolescent obesity and substance use.   In 2011, NIH called for researchers to identify the correlates of obesity, in particular suggesting the importance of identifying associations between obesity and risk taking behaviors while assessing if correlates are similar across subgroups of the population. 

Methods:  Data came from the Centers for Disease Control and Prevention’s national data set, Youth Risk Behavior Surveillance System, 2011.  The YRBS is a randomly administered survey given to a representative sample of adolescents ages 12-18 in the United States to monitor health-risk behaviors.  For this study, substance use is operationalized as use or no use within the past 30 days for alcohol, tobacco, marijuana, and cocaine.  Students who are obese (BMI ≥ 95^th percentile) were compared with those who were in the healthy weight category (BMI in 5^th – 84^th percentile).  Logistic Regression was used to evaluate if adolescent substance use correlated with being obese and to examine the moderator effects of gender and race, while controlling for age.  For the moderator analysis, interactions were tested between gender and any substance use as well as between race/ethnicity and any substance use in the presence of their main effects. 

Results:  14,285 students were included in the original data set.  Based on self-reported BMI, 67.9% were in the healthy weight category, and 13.1% were in the obese category.  Reports of alcohol and cocaine use in the past 30 days revealed no differences between the obese and healthy weight students.  There was a positive association between tobacco use and obesity and a negative association between marijuana use and obesity (OR = 1.70, 95% CI = 1.25–2.30; OR = 0.66, 95% CI = 0.48–0.91 respectively).  Despite evidence that boys and girls have different substance use patterns and rates of obesity, no gender interaction effects were found.  There were, however, statistically significant interaction effects between race and tobacco use (p<.05).  African-American students who report tobacco usage were 7.77 more likely to be obese than white students who report smoking.  Latino students who report tobacco use, however, were only .84 times as likely to be obese compared to white students who report tobacco use. 

Discussion:  Knowing the relationship between obesity and substance use could impact how we design obesity intervention and prevention efforts for adolescents.  In this study, adolescents who reported tobacco use had greater odds of being obese, while those who reported marijuana use had less odds of being obese.  Race moderated the relationship between reported tobacco use and obesity.  Overall, despite the modest statistically significant effects that were found, the differences in obesity rates among youths who use substances and those who do not may not warrant differences in obesity prevention or intervention efforts.