Higher Fitness and Lean Mass Linked to Less Anxiety and Depression in Children

Childhood anxiety and depression are increasingly prevalent in the United States, with rates rising nearly 30% between 2016 and 2020. More than half of all adult mental health disorders originate in childhood or adolescence, making early identification of risk and protective factors critically important. Despite this urgency, few studies have examined how specific components of body composition — particularly visceral adipose tissue (VAT) versus lean mass — relate to mental health in preadolescent children. This study from Northeastern University is the first to use gold-standard DXA scanning and VO2peak testing together in this age group.

The study enrolled 207 children (mean age 10.0 years; 57.5% male) from the Greater Boston area between 2019 and 2023. All participants were free of prior mental health diagnoses. Body composition was assessed via dual-energy x-ray absorptiometry (DXA), capturing body fat percentage (BF%), VAT volume, and total lean mass. Cardiorespiratory fitness was measured using a modified Balke treadmill VO2peak protocol. Anxiety was assessed with the State-Trait Anxiety Inventory for Children (STAIC-T) and depression with the 12-item Child Depression Inventory (CDI-2). Multivariable hierarchical regression controlled for age, sex, race, pubertal status, and mother's education.

For anxiety, BF% was positively associated (β = 0.15; p = .04), as was VAT (β = 0.15; p = .04). Lean mass was inversely associated with anxiety (β = −0.16; p = .02), as was VO2peak (β = −0.19; p = .01). For depression, the strongest predictor was VAT (β = 0.27; p < .001), with lean mass (β = −0.16; p = .03) and VO2peak (β = −0.16; p = .03) again showing protective associations. Notably, BF% was not significantly associated with depression in multivariable models, suggesting that the location of fat — specifically visceral — matters more than total adiposity for depressive symptoms.

The differential finding between BF% and VAT is clinically meaningful. While total body fat was associated with anxiety, visceral adipose tissue — the metabolically active fat surrounding abdominal organs — was the more consistent predictor across both anxiety and depression. This aligns with literature linking VAT to systemic inflammation and metabolic dysfunction, which may influence neurobiological pathways involved in mood regulation. The protective roles of lean mass and VO2peak suggest that muscle tissue and cardiovascular conditioning may buffer against mental health risk, possibly through neuroendocrine and anti-inflammatory mechanisms.

These findings carry significant implications for pediatric health policy and clinical practice. Screening for body composition beyond BMI — using tools sensitive to VAT and lean mass — could help identify children at elevated mental health risk before symptoms become clinically significant. Interventions promoting aerobic fitness and muscle development in school-aged children may simultaneously address physical and psychological well-being. The cross-sectional design precludes causal inference, and the sample was drawn from a volunteer cohort in Greater Boston, limiting generalizability. Nonetheless, the use of criterion-standard measurement tools strengthens the validity of these associations and provides a strong foundation for longitudinal follow-up.