Our findings yield important insights into the relationships between body weight status and risk and protective factors among adolescents. Cross-sectionally, BMI was only associated with depression at the beginning of seventh grade. However, by the end of eighth grade, cross-sectional analyses indicate that depression, binge drinking; ATOD use; and fighting were all significantly associated with BMI. These results suggest that as children age, the associations between increased levels of risk behaviors and increased body mass index become more pronounced. In addition, this transition through early adolescence appears to be a critical age for the development of these adverse behavioral profiles with dramatic increases of 200–400% across a number of substance use behaviors.
This study was also able to explore the temporality of the relationship between BMI and risk and protective factors. Longitudinally, increased levels of ATOD use, fighting, depression, and optimism at the beginning of seventh grade predicted greater increases in BMI by the end of eighth grade. However, BMI at the beginning of seventh grade did not predict the adoption of any of the risk and protective factors by the end of eighth grade. This may suggest that adolescents who have increased BMI z-scores compared to their peers are not more likely to begin engaging in risk behaviors or develop depressive symptoms over time. In addition, having a higher BMI in seventh grade does not appear to affect future changes in optimism or sense of spirituality. However, those adolescents who have higher rates of ATOD use, fighting, and depression in seventh grade are more likely to experience greater gains in body mass indices in eighth grade than adolescents who have lower rates of these behaviors. In addition, adolescents who are less optimistic in seventh grade may also be at higher risk of larger increases in BMI z-score in eighth grade.
These findings suggest that early engagement in risk behaviors and higher levels of early depressive symptoms may be some of the first indicators of a youth’s predisposition to engage in less healthful behaviors in general. Practitioners may play a key role in screening for these factors and discussing the hazards of health risk behaviors (such as substance use) with children and adolescents as a part of routine visits, as recommended by the American Academy of Pediatrics [30
]. Other important interventions sites include home and schools, where parents and teachers may include discussions of these behaviors in their daily routines. In addition, other factors related to child development may be associated with the initiation of risk behaviors and help account for a clustering of riskier behaviors in adolescence. Unhealthy parent-child relationships, social isolation, or stress may stimulate a coping response that manifests as engaging in risk behaviors including ATOD use and then may develop into poor eating and activity behaviors leading to unhealthy excess weight gain.
Previous literature indicates that overweight adolescents report less favorable psychosocial characteristics, such as lower self-esteem [34
]. By observing the cross-sectional associations between risk behaviors with higher BMI, one might be led to believe that heavier teens may demonstrate lower self-esteem and as a result are drawn into substance use and other risk behaviors as a coping mechanism. However, our longitudinal findings yield insights into this relationship and indicate that it is not overweight adolescents who begin to engage in risky behaviors, but rather that it is the teens engaging in risky behaviors who then experience larger gains in BMI (in comparison to their non-risky counterparts). Thus, it may be that risk-taking teens are drawn engaging in less healthy weight-related behaviors because of factors such as the norms within their social networks, decreased concern for overall health, and increased stress levels. Future research examining the mediators of these relationships (as well as the underlying characteristics differentiating who develops these unhealthy behavioral patterns as compared to who does not) will be key in better understanding the causal roots of behavioral patterning, and developing effective and targeted intervention strategies to promote overall healthy lifestyle characteristics at this critical age.
The time period from the beginning of seventh grade to the end of eighth grade appears to be a time of dramatic increases in the prevalence of substance use among these adolescents. The rates of use in this study were similar to national rates in the same year (2000) for smoking (14.9% vs. 14.6% respectively). However, in this study, rates of alcohol use (29.7% vs. 22.4%) and marijuana use (12.0% vs. 9.1%) were marginally higher while binge drinking was marginally lower (10.7% vs. 14.1%) in our sample compared with national data [3
]. Therefore, this study may provide valuable insight into the time period when many adolescents first transition into substance use. These increases may suggest that during this time period youth are exposed to stressors which may trigger substance use behaviors as a way to cope with stress or other environmental stimuli. These early substance use behaviors may be the hallmark of poor coping skills, serving as an early warning sign for the later development of a wide array of risk behaviors, including not only substance use but also sedentary behaviors, poor eating habits, and other unhealthy characteristics. Furthermore, substantial evidence exists to indicate that risk behaviors (such as alcohol use) [35
], as well as weight status [36
] show a strong degree of tracking from adolescence into adulthood. Therefore, these adolescent behavior patterns are not transient in nature and likely have an important influence on long-term behavior patterns.
This research has several strengths. Using longitudinal models allowed us to move beyond the cross-sectional analyses to a more comprehensive view of the relationships between BMI and measures of risk and protective factors. By examining the temporal association between risk and protective factors and BMI hypotheses regarding how risk behaviors may predispose youth for weight problems were developed and tested. The analyses accounted for school as a random effect and adjusted for baseline values in the longitudinal analyses. Additionally, this study utilized a large cohort of early adolescents to explore relationships not previously tested.
This study does have some limitations. The outcome variable in this study was based on the self report of BMI. While this measure is not the gold standard, self reported BMI has been found to be valid and highly reliable among both adolescents and adults [37
]. Also, behaviors related to BMI, such as diet, caloric intake, and physical activity levels were not examined. Future studies may want to explore the associations of these variables with the risk and protective factors to determine if both eating and activity are related or if one variable drives the association. This study was only able to incorporate the use of two protective factors, spirituality and optimism, as these were the only protective factors measured on the survey. Future research should incorporate additional protective factors such as parenting, peer/social support, school and/or community involvement and self-esteem. Additionally, as the possible trigger factors for these behaviors may be stress and poor coping behaviors, studies which also measure these important potential exogenous variables are needed. While this was a longitudinal study, only two time points were used. Future studies should examine the temporal associations between BMI and these risk and protective factors for a longer time period into adolescence to see if the associations hold over time and possibly even grow in magnitude. This study was able to use a large cohort of early adolescents to explore the hypotheses tested; however, a majority of this sample was Caucasian limiting the generalizability of the findings. Additional studies in more diverse populations are needed to see if race/ethnicity moderates these associations.
Interventions to alter risk and protective factors at younger ages may have an effect on excess weight gain later in life. The results of this study also show that the time period between the beginning of seventh grade and the end of eighth grade may be critical for substance use interventions as the prevalence of these behaviors doubled to quadrupled during this time. Future studies are needed to replicate these findings as well as extend the analyses into later ages to see how these relationships change or remain the same as youth move into high school. Finally, studies that explore how the associations are moderated by various individual-level characteristics, such as gender and race/ethnicity, are needed to determine if there are important sub-group differences in the relationships between weight status and health promoting and health compromising behaviors.