A study from January made headlines again this month, focusing on whether one workout per week can help reduce belly fat. It’s worth taking a closer look than most coverage did.
What?
Researchers led by Parco Siu in Hong Kong assigned 315 inactive adults with central obesity to 3 groups: one group performed one workout a week, another performed 3, and the third attended health education classes. After 16 weeks, the once-a-week group lost 0.8 kg of fat compared to the control, while the 3-times-a-week group lost 1.0 kg. The difference between the 2 exercise groups was too small to be significant. Both groups reduced their waist size by about 2 cm. The study was published in Nature Communications.
There are two important details that most reports missed. The exercise involved supervised treadmill sessions: 4 intervals of 4 minutes each at 85-95% of peak heart rate, with 3 minutes of easy walking between intervals. For the once-a-week group, the session meant doing 3 of these blocks in a row with rest breaks, making it almost 2 hours at the gym, not just a long walk.
So what?
The main difference between the groups was in fitness. The once-a-week group improved their VO2 peak by 1.5 ml/kg/min, while the 3-times-a-week group improved by 2.6. 16 weeks after the training ended, only the 3-times-a-week group still had better fitness than the control group. By then, the fat loss was gone, but both groups kept their smaller waists.
I’ve said before that VO2 max is the best measure of how long you’ll live and how well you’ll function. From that perspective, the headline is only partly true. The once-a-week plan matched the others for fat loss, but it didn’t keep up in fitness; fitness was the lasting benefit at week 32.
The other side is important too. For living longer, how you spread out your workouts might not matter much. A 2025 review of 21 studies found that people who exercise only on weekends and those who exercise more regularly both experienced similar reductions in death rates. If you can only fit in one session a week, it’s still worth doing.
The real difference came from working at 85-95% of your peak heart rate.
Now what?
Try the workout as it was tested: start with 5 minutes of easy effort, then do 4 rounds of 4 minutes hard and 3 minutes easy, and finish with another 5 minutes of easy effort. The whole session takes about 35 minutes.
‘Hard’ means you shouldn’t be able to finish a sentence. If you can talk easily during the 4-minute intervals, you’re not pushing hard enough. You don’t need a heart rate monitor for this.
Aim for 3 sessions a week if you can, since that group kept their fitness gains. The study didn’t test 2 sessions a week, so I can’t speak to that.
If your week gets busy, still try to fit in at least one session. Even one workout was better than just attending the education class.
Don’t let the scale be your only measure. Choose a set route or stairwell, time yourself today, and check your progress again in 8 weeks.
8 weeks from today is October 7. Mark your calendar for your retest.
Stay healthy.
Andre