Skipping strength training
There are plenty of reasons to love (or at least tolerate) cardio—it torches calories, improves endurance, and reduces your chances of heart attack and stroke —but make sure you’re incorporating weights into your workouts, too. “We all begin to lose muscle mass around age 30, and this process accelerates at age 40,” says Caroline Apovian, MD, director of the Nutrition and Weight Management Center at the Boston Medical Center.
The problem, she explains, is that muscle mass plays a big role in your basal metabolic rate—the amount of calories you burn at rest—so when you lose muscle mass, your metabolism slows down. (If you’ve noticed it’s suddenly harder to lose weight, that could explain why.) Strength training twice a week (with these 5 essential movements) can help you rebuild muscle and get your metabolism back up to speed.