Fit in 15 minutes of weight training three days a week to overcome the “energy gap” that may make you gain weight.

Some quick exercises you can do almost anywhere may keep you from gaining weight.

RODALE NEWS, EMMAUS, PA—A little bit of weight training can boost your daily calorie burn, perhaps keeping you from gaining weight, according to research published the journal Medicine & Science in Sports & Exercise in 2009. College students who lifted weights three times a week for 15 minutes or so per session saw serious boosts in energy expenditure, which helps burn fat and manage weight, says lead author Erik Kirk, PhD, assistant professor in the Department of Kinesiology and Health Education at Southern Illinois University, Edwardsville. And the benefit lasted long past their workouts. “The fact that increases in daily energy expenditure were still present three days after the last resistance training session is important,” he says. “The minimal resistance-training protocol described in this study may provide an attractive alternative in busy young adults, due to the minimal time commitment.”

THE DETAILS: The study researchers took 39 overweight young adults (average age of 21) and divided them into a resistance-training group and a nonexercising control group. The resistance group worked out three times a week for six months, taking just over 11 minutes to complete all nine exercises. Both groups were told to continue eating their normal diets. At the end of the experiment, the resistance-training group had increased their 24-hour energy expenditure by 4 percent, twice that of the control group, and the researchers found that the effect lingered for up to three days after an exercise session—good news if you can only fit in a workout once every few days. And even though neither group changed their diets, the resistance-training group warded off gains in fat mass during the study, while the control group saw a slight (2.3 percent) increase in theirs (though neither group lost significant amounts of weight).

WHAT IT MEANS: Adding a mere 45 minutes of weight training to your week could boost your body’s fat-burning power and prevent you from gaining weight. Researchers estimate that an “energy gap”—the difference between calories eaten and calories burned—of only 420 kilojoules per day may be responsible for packing on pounds in 90 percent of the population, the authors write. In this study, the short-workout resistance trainers burned an extra 520 kilojoules per day, which would cover that energy gap and then some.