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

Once-weekly HIIT significantly reduced total body fat mass compared to control at week 16.

• Adjusted mean difference for H1 vs. CON: -0.8 kg (95% CI: -1.4 to -0.2), P = 0.0107
• Participants were randomly assigned in a 1:1:1 ratio with n = 105 per group
• Intervention lasted 16 weeks with outcomes assessed at baseline, week 16, and week 32
• The once-weekly HIIT group performed 75 minutes of HIIT in a single session per week ('weekend warrior' approach)

Thrice-weekly HIIT significantly reduced total body fat mass compared to control at week 16.

• Adjusted mean difference for H3 vs. CON: -1.0 kg (95% CI: -1.6 to -0.5), P = 0.0003
• The thrice-weekly HIIT group also performed a total of 75 minutes of HIIT per week, distributed across three sessions
• The control group received biweekly health education classes
• Total body fat mass was the primary outcome measure

No study-related adverse events were reported across any of the intervention groups.

• This finding applied across all three groups: once-weekly HIIT (H1), thrice-weekly HIIT (H3), and control (CON)
• The trial was conducted as a single-center, assessor-blinded, three-group, randomized controlled trial in Hong Kong
• The total sample size was 315 participants (105 per group)
• The 16-week intervention period included high-intensity interval training in both active groups

Both HIIT frequency conditions (once and thrice weekly) produced comparable reductions in fat mass relative to control, suggesting frequency can be compressed without losing efficacy.

• H1 vs. CON: -0.8 kg and H3 vs. CON: -1.0 kg, with overlapping confidence intervals (-1.4 to -0.2 and -1.6 to -0.5, respectively)
• Both groups performed an equal total weekly volume of 75 minutes of HIIT, differing only in session frequency distribution
• The 'weekend warrior' once-weekly approach was explicitly tested as a therapeutic model for reducing body adiposity
• The study population consisted of adults with overweight and central obesity

The trial was designed to examine HIIT delivered via a 'weekend warrior' approach versus standard multi-session frequency in a population with central obesity.

• This was a single-center, assessor-blinded, three-group, randomized controlled trial conducted in Hong Kong
• Participants were randomized in a 1:1:1 ratio to H1, H3, or CON groups with n = 105 per group
• The intervention lasted 16 weeks with follow-up assessment at week 32
• The study was registered at ClinicalTrials.gov (NCT04887454)
• Obesity was framed as a global public health crisis aggravated by high prevalence of physical inactivity