A few minutes of brief, intense exercise may be as effective as much lengthier walks or other moderate workouts for incinerating body fat, according to a helpful new review of the effects of exercise on fat loss. The review finds that supershort intervals could even, in some cases, burn more fat than a long walk or jog, but the effort involved needs to be arduous.

Studies show that interval workouts can improve aerobic fitness, blood sugar control, blood pressure and other measures of health and fitness to the same or a greater extent than standard endurance training, such as brisk walking or jogging, even if it lasts two or three times as long.

Only a few past studies have directly compared the fat-burning effects of endurance training with those of short interval workouts, however, and their results have been inconsistent. Some indicate that intervals prompt significant fat loss and others that any losses are negligible when compared with the effects of endurance training.

But those studies have almost all been small and short-term. They also used many different approaches to interval and endurance exercise, making the findings difficult to interpret.

So, for the new review, published in The British Journal of Sports Medicine, researchers from Brazil and Britain decided to pull together as much data as possible from all of the existing, high-quality studies looking at intervals and body fat. They eventually found 36 studies that involved randomised experiments — not surveys or other epidemiological data — comparing the effects of endurance training with those from interval workouts.

The experiments had to have lasted at least a month and included body-composition measurements at the start and finish, even if changes to body fat had not been the primary focus of the study.

The moderate-exercise routines used in the studies varied considerably, with some involving walking and others jogging, cycling or swimming. In general, the endurance-style workouts lasted for about 40 minutes.

The interval sessions likewise differed from one study to the next, but most involved intervals lasting for a few minutes at a time, at a pace just below all-out effort, which is typical of HIIT. Others required a few seconds of absolutely all-out exertion, an approach the researchers dubbed sprint-interval training, or SIT. Then the researchers simply compared fat loss after the different exercise programmes.

The results should be encouraging for anyone who exercises. Both moderate training and intervals led to reductions in body fat, the researchers found. These reductions were absolute, meaning that people shed some of their actual fat mass, and also relative, meaning that they lowered the percentage of their body mass that was fat. The changes also for the most part occurred whether or not people lost a noticeable amount of overall weight, suggesting that they might be losing fat while gaining muscle.

Perhaps most important for people drawn to quickie exercise, interval training, especially SIT workouts, often burned more fat, in absolute terms, than prolonged, moderate exercise, with interval trainers dropping an average of about 1.5kg of fat versus about 1.1kg for moderate exercisers. Not much difference in real-world terms.

In fact, the primary takeaway of the review could be that, “due to the similarity of outcomes, there can be flexibility in choice of exercise approach,” for anyone hoping to trim fat, said James Steele, an associate professor of sport and exercise science at Solent University in Southampton, England, who conducted the review with colleagues from the Federal University of Goiás in Brazil and other institutions.

Plan your workouts around your preferences and schedules, he said, and not concerns about which type of exercise might better trim fat.

In general, the message is, work out how you like, Steele said. “If you prefer longer yet easier-effort exercise, then go for it,” he said. “If you want to pump it up in a HIIT session, be my guest.”