This medium-intensity, multicomponent behavioral intervention resulted in a modest decrease in weight status among overweight teen-aged girls (−0.15 in BMI z score among intervention participants compared with −0.08 among usual care participants). To our knowledge, this is the first study to demonstrate the efficacy of a behaviorally based intervention specifically targeting teen-aged girls and demonstrating a sustained effect (at 12 months) beyond the active 5-month intervention. Those in the intervention group reported more frequent family meals and less fast-food consumption. There were no other significant differences in reported health behaviors, and no indication that the intervention increased disordered eating practices. Among intervention participants, changes between baseline and posttreatment (6 months) in the magnitude of screen time reduction (~5 hours per week) and reduction in reported energy consumption (a decrease of 240 kcal/day) is consistent with changes considered clinically significant by most PCPs. However, given the high variance for these variables, there were no statistically significant differences between the intervention and usual care groups.
Despite the statistical significance of our primary study outcome (BMI z
score), the weight reduction magnitude was modest (Cohen’s d
= −0.27 for BMI percentile and −0.18 for BMI z
score), suggesting that a more intensive intervention might achieve more clinically significant outcomes. Previous primary care interventions targeting adolescents found somewhat larger effects,25,26
although these results may not be comparable because participant populations were at least 50% male and 1 study25
included younger school-aged children. Furthermore, our participants reported frequent dieting and use of professional weight management services in the 6 months before study enrollment, so they likely had previously adopted some weight management strategies—and therefore achieved more modest effects than those observed in overweight teen boys, who are less likely to report previous weight control attempts.57,58
A modest proportion (17%–18%) of participants in both study arms reported using ancillary professional services for weight control during the active intervention. Furthermore, our participants had high overall BMI at study onset (>97th percentile for age and gender on average). Therefore, our sample may have been treatment resistant, as more severely obese youth are significantly more likely to have persistent weight problems as adults59
and obtaining sustained decreases in obesity in this population has proved difficult.60
Finally, because our pilot work for the study suggested substantial teen and parent sensitivity to the teen’s identification as overweight, we purposefully emphasized goals to improve body image and self-esteem while learning about healthy choices for eating and exercise, and explicitly de-emphasized weight management. Our results suggest that body image was improved by the intervention.
There were important differences in our intervention approach that, although purposeful, may have attenuated its overall impact. Unlike the vast majority of behavioral weight loss interventions, we de-emphasized calorie counting. We anticipated that dietary changes related to decreasing energy density of consumed foods and establishing healthier eating patterns would produce more achievable and sustainable results; unfortunately, these guidelines may not have been adequate in achieving clinically meaningful caloric reductions and sustained weight loss. Finally, rather than adopting a more family-centric approach, we purposely focused on helping teens manage their weight with more autonomy. Yet previous interventions, particularly with younger children, have demonstrated that the most robust weight management occurs when parents also adopt targeted lifestyle changes.61
This finding suggests that an intervention which actively targets parent lifestyle changes (rather than focusing, as this intervention did, primarily on supporting the teen’s efforts) may have the benefit of allowing teen autonomy while supporting healthy weight management and lifestyle changes within the broader family.
A limitation of the study was the lack of racial/ethnic and socioeconomic diversity among study participants, particularly given known health disparities related to obesity.1,62,63
As children of working insured parents, study participants represent this sizable sector of the population. Yet, we acknowledge that the results might not be generalizable to other subpopulations.
A strength of our study was our inclusion of participants with comorbid mood and disordered eating practices; we believe this was important to increase generalizability given the higher incidence of such problems among overweight youth. Also, until recently, most research-based youth obesity interventions have been conducted in university settings and therefore may not have been representative of efforts in the community. Increasingly, however, health plans are adopting practices to identify members who may benefit from similar health behavior interventions; therefore, our efforts to expand eligibility may render our results more generalizable.