Can one intense workout per week keep you healthy? Here's the science.
What the study tested
Published in Nature Communications, the study followed 315 adults who were overweight or had central obesity for 16 weeks. Researchers assigned participants to one of three groups: a single weekly HIIT workout, the same exercise spread over three sessions, or health education classes without exercise.
Both exercise groups completed the equivalent of three 25-minute HIIT blocks, each involving four minutes of hard effort and three minutes of easier activity. The once-weekly group did all three blocks in one visit; the other group completed one block per visit across the week. Workouts included a warm-up and cool-down.
Body fat and fitness results
Both workout groups lost more body fat than the control group. The once-weekly participants lost about 1.75 pounds more than controls, while those exercising three times per week lost 2.2 pounds more. Waist circumference also improved significantly in both exercise groups compared with the control group.
Fitness gains differed: cardiorespiratory fitness rose roughly 6 percent in the once-weekly group and about 11 percent in the three-session group. Diaz said that more frequent exercise can prompt greater adaptation in the heart, blood vessels and muscles. Neither group reported exercise-related injuries, and Diaz described the fat reductions as modest.
Who may benefit most
For people mainly focused on fat loss, a weekly workout may be enough to make a difference. Diaz said spreading activity across the week may be a better choice for those seeking greater fitness and overall health.
He described the once-weekly approach as most suitable for generally healthy people who are short on time and might otherwise miss exercise. The study supports the potential value of this schedule, but its findings do not mean it is the best option for everyone.
Key points
- Both weekly and three-times-weekly HIIT groups lost more body fat than the control group.
- The three-session group improved cardiorespiratory fitness more than the once-weekly group.
- Diaz says the consolidated approach may suit healthy people with limited time.
- People with diabetes or hypertension should aim to be active every day.