Physical Activity as a Mediator in the Relationship Between Body Image Perception and Low Mood in Adolescents

Body image (BI) plays a critical role in mental health, with negative perceptions often linked to feelings of low mood. Physical activity (PA) has been shown to enhance self-acceptance and reduce negative emotions, suggesting it may help mitigate the impact of BI on low mood. This study examines the relationship between BI and low mood among adolescents, and explores the role of PA as a mediator in this relationship. The study had a cross-sectional design. Data were collected from 154,183 adolescents (average age 13.6 ± 1.6 years) across 43 countries, using the 2017/2018 Health Behaviour in School-aged Children (HBSC) survey. BI was assessed through self-perceived body size, low mood was measured on a scale from "about every day" to "rarely or never", and PA was evaluated by the number of days per week participants engaged in at least 60 min of activity. The study used multinomial logistic regression and a mediation model to analyze the relationships of BI, PA, and BMI with low mood. The multinomial logistic regression showed that daily PA reduces the risk of low mood, especially with higher PA frequency, such as PA on 6 days (OR = 0.72) and PA on 5 days (OR = 0.86). Age, BMI, BI, and sex also influence low mood, with males showing lower odds (OR = 0.40 to 0.77), normal weight individuals having a reduced risk, and thinner individuals having lower odds of low mood (OR = 0.12 to 0.50), with PA partially mediating the relationship between BI and low mood (<i>p</i> < 0.001), contributing to 9% of the total effect. PA partially mediates the relationship between BI and low mood, with a direct negative impact of BI on low mood. In addition, girls, older adolescents, and those with negative BI and irregular PA have a higher risk of low mood.