One workout a week can help you lose weight, new study finds

What if you don’t have to hit the gym every day to lose weight? Sometimes less is more. And that’s exactly what a research team from the School of Public Health at the LKS Faculty of Medicine, the University of Hong Kong (HKUMed), found.

In a recent study by HKUMed researchers, they found that a particular activity performed once a week is better than working out three days a week. The findings are published in Nature Communications.

Obesity is a growing health concern across the globe. Excessive fat accumulation is a chronic condition that has an adverse effect on health. Excess adiposity, particularly around the abdomen, is linked to many illnesses, including cardiovascular disease, metabolic disorders and increased mortality risk. For people struggling with obesity, regular exercise is crucial; however, most grapple with consistency.

People who struggle with obesity often find it challenging to exercise daily. And that’s exactly where interval training comes in. This involves alternating periods of vigorous exercise with lower-intensity, active-recovery exercise. This approach has proven to be effective and time-efficient in reducing total body weight and visceral fat, compared with traditional moderate-intensity training. However, standard exercise guidelines often recommend interval training three times a week, which may not be practical for individuals with time constraints and limited access to exercise facilities.
Previous research has found that being a ‘weekend warrior’, which means squeezing everyday workouts into one or two days, has a positive effect. However, there is limited evidence to support the effectiveness of this strategy.

Professor Parco Siu Ming-fai, Professor and Head of the Division of Kinesiology at the School of Public Health, HKUMed, wanted to know whether once-weekly interval training can be as effective as the traditional thrice-weekly regimen. To understand this, the researchers conducted a rigorous trial in Hong Kong involving 315 Chinese adults aged 18 and older. The participants were overweight and had central obesity. They were studied between September 2021 and September 2024. The participants were assigned to three groups: a once-weekly interval training group, a thrice-weekly interval training group, or a control group.
The control group attended a 2.5-hour health education session every two weeks over four months. On the other hand, participants in the interval training groups completed a total of 75 minutes of interval training per week. This was either in a single session or divided into three sessions. The participants’ body fat mass was measured before the study, at 16 weeks, and at 32 weeks. The researchers were surprised to find that both the once-weekly and thrice-weekly interval training groups had similar results.

At the 16-week mark, both the once-weekly and thrice-weekly interval training groups showed similar reductions in total body fat mass, fat percentage and waist circumference compared with the control group. The researchers also found that cardiorespiratory fitness improved equally in both groups. The benefits held up at the 32-week follow-up assessment.
“While thrice-weekly interval training remains a commonly recommended approach for the therapeutic management of excess adiposity, our findings show that once-weekly interval training offers similar benefits and represents a practical exercise strategy. For many adults with central obesity who struggle to balance work, study, family and other commitments, time constraints are a primary barrier to exercising multiple days per week,” Professor Siu said.
He added, “Instead of relying solely on high-frequency exercise prescriptions, once-weekly interval training can be considered a feasible and effective alternative.”