The mediating effect of depression and eating behaviours on the relationship between smartphone addiction and obesity in adolescents

The widespread use of smartphones among adolescents has led to growing concerns about their potential effects on both mental and physical health. Excessive smartphone use among adolescents has been linked to depression, sedentary behavior, and unhealthy eating habits, all of which increase obesity risk. Yet, the mechanisms connecting smartphone addiction to obesity especially through depression and eating behaviors remain unclear. A cross-sectional design was conducted with 1,050 adolescents from five high schools in Eastern Turkey between April and June 2025. Data were collected using the Smartphone Addiction Scale–Short Version (SAS-SV), Kutcher Adolescent Depression Scale–11 (KADS-11), and Adolescent Eating Behavior Scale (AEBS). Anthropometric measurements (height and weight) were taken to calculate BMI-for-age z-scores based on WHO standards. Data were analyzed using descriptive statistics, Pearson correlations, multiple regression, and mediation analysis with Hayes’ PROCESS macro (Model 4), controlling for demographic covariates. Smartphone addiction was not directly associated with obesity (c’=0.04, p = 0.48). However, significant indirect effects were observed through depression (b = 0.04, 95% CI [0.02–0.07]) and eating behaviors (b = 0.07, 95% CI [0.04–0.11]), with a total indirect effect of b = 0.11 (95% CI [0.07–0.16]). Depression was positively associated with BMI-z scores, whereas unhealthy eating behaviors were negatively associated with them. The overall model explained 19% of the variance in BMI-z. These findings indicate that smartphone addiction increases obesity risk indirectly through depressive symptoms and unhealthy eating patterns rather than through direct effects. Interventions targeting adolescent obesity should incorporate strategies that enhance emotional regulation, promote healthy eating behaviors, and improve digital self-regulation skills. Integrated school-based programs combining mental health support, nutrition education, and digital health literacy may be effective in reducing the dual risks of smartphone addiction and obesity.