Tired of sweating all over every piece of cardio equipment at the gym and still getting zero love from the scale? You need more iron. Not in your diet—in your hands. According to the National Center for Health Statistics, a mere 21 percent of women strength train two or more times a week. What you don't know: When you skip the weight room, you lose out on the ultimate flab melter. Those two sessions a week can reduce overall body fat by about 3 percentage points in just 10 weeks, even if you don't cut a single calorie. That translates to as much as three inches total off your waist and hips. Even better, all that new muscle pays off in a long-term boost to your metabolism, which helps keep your body lean and sculpted. Suddenly, dumbbells sound like a smart idea. Need more convincing? Read on for more solid reasons why you should build flex time into your day.
Torch Calories 24/7
Though cardio burns more calories than strength training during those 30 sweaty minutes, pumping iron slashes more overall. A study in The Journal of Strength and Conditioning Research found that women who completed an hour-long strength-training workout burned an average of 100 more calories in the 24 hours afterward than they did when they hadn't lifted weights. At three sessions a week, that's 15,600 calories a year, or about four and a half pounds of fat—without having to move a muscle.
What's more, increasing that afterburn is as easy as upping the weight on your bar. In a study in the journal Medicine & Science in Sports & Exercise, women burned nearly twice as many calories in the two hours after their workout when they lifted 85 percent of their max load for eight reps than when they did more reps (15) at a lower weight (45 percent of their max).
There's a longer-term benefit to all that lifting, too: Muscle accounts for about a third of the average woman's weight, so it has a profound effect on her metabolism, says Kenneth Walsh, director of Boston University School of Medicine's Whitaker Cardiovascular Institute. Specifically, that effect is to burn extra calories, because muscle, unlike fat, is metabolically active. In English: Muscle chews up calories even when you're not in the gym. Replace 10 pounds of fat with 10 pounds of lean muscle and you'll burn an additional 25 to 50 calories a day without even trying.