Feasibility and efficacy of adding high-intensity interval training to a multidisciplinary lifestyle intervention in children with obesity—a randomized controlled trial

Multidisciplinary lifestyle interventions for children with obesity in Denmark often include recommendations regarding physical activity, but no structured exercise program. We hypothesized that adding high-intensity interval training (HIIT) to a multidisciplinary lifestyle intervention would improve BMI z-score (primary outcome), waist circumference, blood pressure, and health-related quality of life (HRQOL). This randomized controlled trial included 173 children and adolescents with obesity. Participants were allocated to 12-months lifestyle intervention (N = 83), or 12-month lifestyle intervention accompanied by a 12-week HIIT program (N = 90). HIIT consisted of three weekly sessions and included activities eliciting intensities >85% of maximal heart rate. Attendance rate for the 3-months HIIT intervention was 68.0 ± 23.2%. Dropout was lower in HIIT compared to control at three months (7.8% vs. 20.5%) and 12 months (26.5% vs 48.2%). Changes in BMI z-score did not differ between HIIT and control at 3 months (Mean Difference (MD): 0.01, 95% confidence interval (CI): −0.09; 0.12, P = 0.82) or 12 months (MD: 0.06, CI: −0.07;0.19, P = 0.34). Across randomization, BMI z-score was reduced by 0.11 (CI: 0.17; 0.06, P < 0.01) at 3 months and 0.20 (CI: 0.26;0.14, P < 0.01) at 12 months. At 3 months, HIIT experienced a greater increase in HRQOL of 2.73 (CI: 0.01;5.44, P = 0.05) in PedsQL Child total-score and 3.85 (CI: 0.96; 6.74, P < 0.01) in psychosocial health-score compared to control. At 12 months, PedsQL Child physical-score was reduced by 6.89 (CI: 10.97; 2.83, P < 0.01) in HIIT compared to control. No group differences or changes over time were found for waist circumference or blood pressure. Adding a 12-week HIIT program did not further augment the positive effects of a 12-month lifestyle intervention on BMI z-score. Adding HIIT improved HRQOL after 3 months, but reduced HRQOL at 12 months. Implementation of HIIT in community-based settings was feasible and showed positive effects on adherence to the lifestyle intervention.