A single, 75-minute session of high-intensity interval training (HIIT) per week may be as effective at burning fat as completing three shorter sessions spread throughout the week, according to research published in the journal Nature Communications. The study, conducted by researchers at the University of Hong Kong, compared the effects of different HIIT frequencies on adults with abdominal obesity.
Participants were divided into two groups. One group engaged in a single 75-minute HIIT session weekly, while the other group split the same amount of exercise into three 25-minute sessions distributed across the week. Each 25-minute session included four 4-minute high-intensity intervals interspersed with three-minute rest periods.
Measurements of total body fat mass, body fat percentage, and waist circumference were taken at the beginning of the study, after four months, and again at eight months. After the initial four months, both groups showed significant reductions in total body fat. The once-a-week group experienced a loss of approximately 2.6%, while the group exercising three times a week lost about 3.5%.
Although the fat loss observed in both groups plateaued after the subsequent four months, participants in both groups continued to see reductions in their waistlines, which is an indicator of visceral fat. This suggests that the total volume of exercise may be more critical for fat loss than how frequently it is performed.
The findings indicate that a "weekend warrior" approach, where exercise is concentrated on one or two days, could be a viable option for individuals facing time constraints. Lead study researcher Professor Parco Siu Ming-fai noted that once-weekly interval training can serve as a practical and effective alternative to solely relying on high-frequency exercise regimens.
Another study mentioned in the notes found that individuals who exercise only on weekends can lower their risk of over 200 diseases to a similar extent as those who exercise throughout the week. HIIT, regardless of its frequency, offers numerous health benefits. These include reduced blood pressure, boosted metabolism, lower blood sugar levels, and increased calorie burn for an extended period post-exercise.
Some interval training sessions can be completed in as little as 20 minutes using minimal equipment. However, the notes also caution that excessive HIIT can be counterproductive, potentially disrupting cortisol levels and leading to decreased activity, lower body temperature, and weight gain.