Combined high-intensity interval training as an obesity-management strategy for adolescents

Effective and safe exercise protocols for obesity management in adolescents are imperative. This study aimed to analyse compliance, efficacy, and safety of combined high-intensity interval training circuit (HIIT) in the management of obesity (including overweight) in adolescents, compared to traditional training (TT). Data from 55 adolescents (47.3% girls) (TT n = 31; HIIT n = 24), aged 12-18 (mean age of 14.3 ± 1.7), with overweight and obesity (median BMI z-score of 2.95), were assessed at baseline and month 6 (Clinicaltrials.gov/NCT02941770). During the 6-month intervention, participants in both exercise groups attended two exercise sessions/week (60 min/session) along with a set of appointments with a paediatrician, nutritionist, and exercise physiologist. Forty-six participants completed the intervention (TT n = 23; HIIT n = 23). Exercise session attendance (≥80%) was significantly higher among HIIT participants (73.9 vs. 13.0%, p < .001). HIIT, but not TT, showed a significant decrease in BMI z-score (d = 0.40, p < .001), body fat mass (BFM, %) (d = 0.41, p = .001), and trunk fat mass (d = 0.56, p < .001), as well as a significant increase in muscle mass (MM, %) (d = 0.28, p = .001) between baseline and 6 months. According to generalized estimating equations, time-by-attendance interactions (instead of time-by group) were found in BMI z-score (β = 0.25, 95%CI: 0.17, 0.33), BFM (β = 2.29, 95%CI: 1.02, 3.56), trunk fat mass (β = 2.94, 95%CI: 1.70, 4.18), and MM (β = -1.16, 95%CI: -1.87, -0.45). No adverse events were reported during HIIT sessions. Although compliance may mediate the impact of an exercise protocol on health-related outcomes, HIIT showed to be safe, with higher compliance compared to TT, which may result in improved outcomes overtime.