Physical activity rather than sedentary behaviour is socially determined in French adolescents with overweight and obesity.

Social differences in prevalence of overweight and obesity among adolescents, known as the weight social gradient, could be explained by differences in behaviours between social classes. This study examined the respective association of physical activity (PA), sedentary behaviour (SB) and weight status with adolescents' socioeconomic status. We used cross-sectional data for 1935 adolescents (13-18 years old) with overweight or obesity who participated in the PRALIMAP-INÉS (PRomotion de l'ALImentation et de l'Activité Physique - INÉgalités de Santé) trial conducted in northeastern France between 2012 and 2015. Adolescents completed the International Physical Activity Questionnaire for PA and SB and the Family Affluence Scale for socioeconomic status. Weight status was assessed by the body mass index (BMI) and BMI z-score. Social gradient of weight status, PA and SB were described according to the Family Affluence Scale (slopes) and evidenced by the linear trend test (p). Adolescents' socioeconomic status was positively associated with PA practice (frequency, vigorous PA and leisure-time PA), but there was no association with their SB. The results confirmed a significant weight social gradient: BMI (ß = 0.37, p < .0001) and BMI z-score (ß = 0.07, p = .0001). The weight social gradient in adolescents was mostly associated with PA (5.7% to 8.1%) rather than SB (2.7% to 5.7%). Nearly 14% of BMI z-scores could be related to a combined PA and SB effect. PA was found an important factor of weight social gradient in adolescence. Actions aimed at preventing weight social inequalities among adolescents could include PA promotion as lever. CLINICAL TRIALS REGISTRY AND NUMBER: ClinicalTrials.gov (NCT01688453).

Universal School-Based Intervention Does Not Reduce Socioeconomic Inequalities in Weight Status among Adolescents.

Background: Differences in weight status by socioeconomic position occur during adolescence and is known as weight social gradient (WSG). The PRALIMAP (Promotion de l'ALIMentation et de l'Activité Physique) trial highlighted that a universal intervention was effective in reducing overweight and obesity prevalence among adolescents. However, its ability to reduce the WSG is unclear. This study aimed to evaluate the impact of the PRALIMAP intervention on the WSG among adolescents. Methods: Data were obtained from 3504 adolescents who participated in the school-based PRALIMAP trial between 2006 and 2009. The PRALIMAP study consisted of three interventional strategies: educational, environmental, screening and care. Weight status was assessed by body mass index (BMI) z-score and overweight and obesity prevalence. The "indice de position sociale des élèves" was used to measure adolescents' socioeconomic status. Linear regression and hierarchical models were used to assess the WSG and its evolution, respectively. Results: Among all adolescents (14-18 years old), significant WSG was identified at baseline: BMI z-score (ß = -0.06; p < 0.0001), overweight and obesity prevalence (ß = -2.86; p < 0.0001). Overall, the intervention conferred no significant reduction in the WSG: BMI z-score (ß = -0.01 [-0.02 to 0.01], p = 0.48), overweight and obesity prevalence (ß = -0.01 [-0.07 to 0.05], p = 0.73). Similar results were observed for adolescents whatever the interventional strategy they benefited from in the PRALIMAP trial. Conclusions: This study provided no evidence that the PRALIMAP universal intervention was effective in reducing the socioeconomic inequalities in weight status among adolescents. Different interventions that account for social differences should be considered to tackle these inequalities.