Performing a longer high-intensity interval training, or HIIT, program with a treadmill once per week could burn body fat at the same rate as spreading that time across three weekly sessions, according to a recent study published in Nature Communications.

The randomized controlled trial, conducted in Hong Kong, involved 315 Chinese adults who were overweight and had central obesity. Participants were assigned to one of three groups: once-weekly HIIT, three-times-weekly HIIT, or a control group receiving health education.

Both HIIT groups completed 75 minutes of HIIT per week. The once-weekly group performed three 25-minute HIIT routines in a single day, with 15- to 30-minute breaks between. The three-times-weekly group completed one 25-minute routine on each of three separate days. All sessions were performed on motorized treadmills, with heart-rate monitoring and supervision by certified trainers.

The study lasted 16 weeks, with follow-up assessments at week 32. At week 16, both HIIT schedules reduced total body fat mass compared with the control group. The once-weekly group lost an average of 0.8 kilograms, and the three-times-weekly group lost an average of 1 kilogram, showing only a minor difference between the two HIIT groups. Both also showed reductions in body fat percentage and waist circumference, along with cardiorespiratory improvements.

The findings suggest that concentrating structured HIIT into one day may be a practical alternative for people who struggle to exercise several times a week.

The authors also noted that the findings may not apply to people with more complex metabolic conditions, such as type 2 diabetes, and that the trial was limited to Chinese adults. Further studies are needed to test whether the results hold across more diverse populations.