The once-a-week workout that may cut belly fat, according to new research

One of the most common reasons people give for not exercising regularly is a lack of time, and public health guidelines that call for spreading moderate activity across most days of the week can feel especially daunting to anyone juggling a demanding job or family responsibilities. A new trial suggests that, for people carrying excess fat around the waist, concentrating that same weekly exercise dose into a single longer session may work almost as well.

The study followed 315 adults with central obesity, meaning excess fat concentrated around the abdomen rather than distributed evenly across the body, over a four-month period. Central obesity is of particular interest to researchers because visceral fat around the waist is more strongly linked to cardiovascular disease and type 2 diabetes than fat stored elsewhere, even in people whose overall body weight falls within a normal range.

Participants were split into groups: one completed a single weekly session of 75 minutes of brisk interval walking, alternating between faster and slower paces, while another spread an equivalent volume of the same exercise across three separate days during the week. A comparison group continued with their usual activity levels, allowing researchers to isolate the effect of the exercise itself.

After four months, both exercise groups showed meaningfully lower body fat percentages, reduced waist circumference, and improved cardiovascular fitness compared with the group that made no changes, and the single weekly session group's results were statistically similar to the group that split the workload across three days. Neither exercise group needed structured gym access, since brisk walking with pace changes can be done outdoors or on a treadmill with minimal equipment.

Interval walking, sometimes called Japanese-style interval walking training, alternates roughly three-minute stretches of brisk walking with three-minute stretches of a more relaxed pace, repeated over the course of the session. The approach has been studied for over a decade as a lower-impact alternative to running-based interval training, particularly for people managing weight, blood pressure or blood sugar.

Exercise physiologists say the finding fits a broader pattern in recent research on physical activity: what appears to matter most for many health outcomes is the total weekly volume and intensity of activity, rather than strictly how that volume is distributed across the week, at least within reasonable limits. That does not mean frequency is irrelevant for every outcome, but for the specific markers measured in this trial, the researchers found little difference between a concentrated and spread-out approach.

The finding has practical implications for public health messaging, researchers say, since a single achievable weekly session may be easier for many people to commit to and sustain than trying to rearrange a busy schedule around three or more separate workouts. Adherence, they note, is often the biggest obstacle to exercise programmes working in real-world settings, regardless of how well-designed the underlying exercise protocol is.

The researchers caution that the single-session approach was tested specifically as brisk interval walking over 75 minutes, not as an equivalent amount of a different, more intense activity crammed into one sitting, and that findings for this particular population, adults with central obesity, may not generalise directly to athletes or people managing other health conditions.

Medical guidelines in most countries still recommend at least 150 minutes of moderate-intensity activity per week, generally advising it be spread across multiple days, partly because concentrated exercise sessions can carry a higher short-term injury risk for people who are not used to sustained physical exertion. Starting gradually and building up intensity over several weeks, rather than attempting a 75-minute session from a sedentary baseline, remains standard advice.

For readers looking to try the approach, the researchers suggest starting with shorter interval walks and gradually building toward the full session length, while treating the specific timing, whether concentrated into one day or split across the week, as a matter of personal preference and practicality rather than a factor that meaningfully changes the underlying health benefit.