How many times have you been told that middle age spread—the weight gain that comes with hitting 40 and beyond—is unavoidable? Well, next time someone starts going on about the inevitable metabolic slowdown, know this: You can turn the ship around. It’s not even that hard.

Metabolic slowdown is a real thing. It’s due to your muscle mass declining—by up to eight percent each decade after age 30 and up to 10 percent after the big 5-0. “You lose about a half pound of lean muscle every year in your twenties, thirties, and forties, and once you hit your fifties, you lose roughly a pound a year,” says Wayne Westcott, Ph.D., an exercise physiologist at Quincy College in Boston. Although researchers aren’t exactly sure how this happens, the leading theory is that your body starts breaking down muscle at a faster rate than it can build it back up again. Muscle is metabolically active, so your metabolism slows as it declines.

So what do you think might reverse the trend? That’s right, more muscle!

Research shows that lifting weights twice a week for 25 minutes will get you the additional brawn to keep your metabolism humming. One study done by Westcott of more than 1,600 people between the ages of 21 and 80 showed a muscle gain of around 3.1 pounds after 10 weeks of resistance training twice a week. “That’s the equivalent of reversing about six years of aging,” says Westcott. The subjects did one set of 12 different exercises, using a high enough weight that they fatigued after eight to 12 reps. Best part is, it didn’t matter whether they were 25 or 75, there were similar results across all age groups. We’re sold!