Q: I’ve heard that in order to burn fat you must exercise moderately for at least 40 minutes, and that vigorous exercise primarily burns sugar, not fat. Does that mean I should avoid high-intensity workouts if I want to lose weight?
A: No. It is true that the body burns a greater percentage of fuel from fat than sugar during prolonged, easy-to-moderate exercise, but the body’s fuel during more vigorous exercise is primarily sugar. Researchers, however, have not determined whether that physiological difference in fuel consumption translates into any meaningful difference in the amount of fat or weight you would lose.
What they do know is that you’ll shed body fat and pounds if you consistently burn more calories than you consume from food and drinks. And the average person can do moderate exercise, such as brisk walking, for a much longer time than a vigorous one like running – and consequently burn significantly more calories overall.
At the same time, more intense exercise can help you shed pounds if you use a popular fitness method called interval training, in which you weave short bursts of vigorous exercise into a session of easier activity. Because the bursts generally do not cause much fatigue, most clients who I work with are still able to exercise for a long time with interval training, and thus burn more calories than maintaining a moderate pace only.
A simple way to incorporate interval training into your fitness program would be to increase your walking, jogging, or hiking pace for 1 minute immediately followed by 2-3 minutes of slower walking, jogging, or hiking. Then, repeat this sequence of 1 fast minute/2-3 slow to moderate minutes for up to 30 minutes three times a week.