A single session of brisk interval walking each week may reduce body fat as effectively as splitting the same exercise across three days, according to a new study from the University of Hong Kong.
The four-month trial, published in the journal Nature Communications, examined 315 adults with abdominal obesity, a buildup of deep visceral fat around the stomach and abdomen. Visceral fat is considered more harmful than fat stored on the arms or legs because it surrounds vital organs and raises the risk of heart disease, diabetes and other serious illnesses.
Researchers focused on interval walking, a workout that alternates very fast walking with short periods of rest.
Participants were divided into three groups. One completed a single 75-minute interval walking session per week. A second group divided the 75 minutes into three workouts across the week. A third group, serving as a control, did not exercise.
Researchers used bone density scans to measure body fat, which provide an accurate reading of the ratio of fat to muscle. They recorded total body fat mass, body fat percentage and waist circumference at three points: before the study began, immediately after the 16-week program, and four months after it ended.
At the 16-week assessment, both exercise groups showed similar improvements. The findings suggest total exercise volume may matter more than how it is distributed across the week, the researchers said.
The study found no significant changes in blood pressure or cholesterol. The authors said this may be because participants' levels were already fairly normal at the outset.
Reductions in waist size lasted at least four months after the exercise program ended, though the advantages in fat loss and weight loss had largely faded by then.
The researchers concluded that once-weekly interval training may be a feasible and effective alternative for people who struggle to fit multiple exercise sessions into their schedules.
"While thrice-weekly interval training remains a commonly recommended approach for the therapeutic management of obesity, our findings show that once-weekly interval training offers similar benefits and represents a practical exercise strategy," said Professor Parco Siu Ming-fai, the study's lead researcher.
"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," Siu said. "Instead of relying solely on high-frequency exercise prescriptions, once-weekly interval training can be considered a feasible and effective alternative."
An estimated 66% of adults in the United Kingdom are classified as overweight or living with obesity. The condition is linked to health risks including type 2 diabetes, heart disease and breathing problems, and costs the National Health Service more than £11 billion a year, in addition to wider losses from reduced productivity and welfare spending.
The NHS recommends that adults get at least 150 minutes of moderate-intensity activity per week, such as brisk walking.
