Maximal fat oxidation training improves mental health in children with obesity: a 2-month randomized controlled trial

Introduction Obesity impairs physical and mental health; exercise training is a crucial intervention strategy. We examined the effect of an 8-week individualized FATmax training program on mental health in children with obesity. Methods Thirty-six school-aged children with obesity (13.1 ± 0.9 years; BMI: 33.4 ± 2.3 kg/m²) were randomized to experimental (EXPG, n = 20) or control (CONTG, n = 16) groups. EXPG completed 4 × 90-min weekly FATmax sessions for 8 weeks; CONTG maintained usual activity. Anthropometrics, cardiopulmonary fitness (VO₂ peak, FATmax rate), and psychological outcomes (self-esteem, anxiety, depression) were assessed pre- and post-intervention. Results EXPG showed significant improvements vs. CONTG: VO₂ peak (+23%), FATmax rate (+66%), and large reductions in central adiposity (all p < 0.001). Mental health significantly improved in EXPG (self-esteem +59%, anxiety −12%, depression −28%; all p < 0.01), with large effect sizes ( η p ² = 0.78–0.94). Changes in mental health strongly correlated with reduced waist circumference ( r = 0.74–0.89) and enhanced VO₂ peak and FATmax rate ( r = 0.72–0.91; all p < 0.01). Discussion A short, supervised, individualized FATmax intervention substantially improves mental health and cardiometabolic health in school-aged children with obesity, plausibly mediated by decreases in central adiposity and improvements in aerobic fitness.