If you’re exercising to trim fat (and who isn’t?) there’s good news: researchers say you’ll lose almost the same amount of weight no matter whether you choose high-intensity interval training, known as HIIT, or more moderate, longer workouts. Researchers reached that conclusion after reviewing 36 randomized experiments studying more than 1,000 participants, young and old, male and female.
Those who chose interval training, especially the all-out exertion that researchers call sprint interval training, often burned more fat than those who favored longer, moderate exercise. The difference in weight loss among the two groups, however, was negligible—one pound. HIIT exercisers lost an average of about 3.5 pounds of fat during most studies, while moderate exercises dropped about 2.5 pounds.
The tiny difference indicates you should feel free to choose either workout you prefer if your goal is to lose weight, says one researcher.
“Due to the similarity of outcomes, there can be flexibility in choice of exercise approach…,” says James Steele, an associate professor of sport and exercise science at Solent University in Southampton, England. Steele conducted the review with colleagues from the Federal University of Goiás in Brazil and other institutions.
“If you prefer longer yet easier-effort exercise, then go for it,” he says. “If you want to pump it up in a H.I.I.T. session, be my guest.”
The review, which was published in January in The British Journal of Sports Medicine, compared the effects of interval workouts to those of moderate intensity. The studies looked at longer endurance training workouts such as jogging, walking, swimming or cycling. This training usually lasted about 60 minutes. The HIIT workouts of strenuous exertion usually lasted half the time, in few minute or second increments followed by short rest periods.
Comparing fat loss after the different exercise programs, reviewers saw that both workouts reduced body fat. Brief intense exercise may be as effective as longer walks or other moderate workouts for trimming body fat. While HIIT could incinerate more fat than a long walk or jog, reviewers found vigorous effort would be demanded. People reduced some of their actual fat mass as well as the percentage of their body mass that was fat. The review concluded that people might be gaining muscle as they lost fat.
Studies reveal that interval workouts can improve aerobic fitness, blood sugar control, blood pressure and other measures of health and fitness as much or more than standard endurance training lasting two or three times as long as HIIT.
The new review in the British Journal of Sports Medicine looks at all the existing, high-quality studies examining intervals and body fat. The reviewed studies used randomized experiments but not surveys or other epidemiological data. Researchers limited their review to experiments lasting at least a month. The studies had to include body-composition measurements at the start and finish.
A few earlier studies have directly compared the fat-burning results of endurance training to short interval workouts, but almost all been small and short in duration. Their differing approaches to interval and endurance exercise made them difficult to interpret.