Once and thrice weekly interval training in adults with central obesity: a randomized controlled trial

Obesity is a global public health crisis that is aggravated and mirrored by the high prevalence of physical inactivity. This single-center, assessor-blinded, three-group, randomized controlled trial in Hong Kong examined the therapeutic value of high-intensity interval training (HIIT) delivered in one session per week via a "weekend warrior" approach versus three sessions per week for reducing body adiposity in adults with overweight and central obesity. Participants were randomly assigned in a 1:1:1 ratio to once-weekly HIIT (H1), thrice-weekly HIIT (H3), and control (CON) groups (n = 105 per group). The interventions lasted for 16 weeks. The HIIT groups performed a total of 75 minutes of HIIT per week (either in one session or three sessions), while the control group received biweekly health education classes. Outcomes were assessed at baseline, week 16, and week 32. The primary outcome was the change in total body fat mass from baseline to week 16. Secondary outcomes were reported in the main text. Compared to CON at week 16, both HIIT groups showed decreased fat mass (adjusted mean differences: H1 vs. CON: -0.8 kg [95% CI: -1.4 to -0.2], P = 0.0107; H3 vs. CON: -1.0 kg [95% CI: -1.6 to -0.5], P = 0.0003). No study-related adverse events were reported. Here, we show that HIIT, performed once- or thrice-weekly, is safe and reduces fat mass in adults with overweight and central obesity. Trial Registration: ClinicalTrials.gov identifier: NCT04887454.