They say age ain’t nothing but a number, but there are some pretty startling stats about what happens to the human body as time passes. “As men age, they can lose five to seven pounds of muscle mass every 10 years starting in their 30s, and more as they approach their 50s,” says Wayne Westcott, Ph.D., professor of exercise science at Quincy College, researcher, and author of more than 20 books on strength training. “They also gain about 10 pounds over the same time frame.” Now, some math: If you go down five or so in muscle, but up 10 overall—that’s 15-plus pounds of fat gained each decade.
As soon as you hear “fat gain” you may be tempted to up your game on the treadmill to burn off a few extra calories. According to the science, though, your time is better spent in the weight room. A little more math: In people who don’t do any resistance training, each pound of muscle burns about six calories per day; so if you have 80 pounds of muscle, that’s 480 calories per day. Add in regular strength training of two or three sessions per week, and those worked-out, in-need-of-repair muscles can burn nine calories per day at rest—a 50 percent increase!—or 630 calories. And that doesn’t count what you work off during the workout itself. Further, resistance training is the only way to reduce (and even reverse) that pesky muscle loss due to aging.
That doesn’t mean you should skip your cardio, though. “With age, people experience a decrease in aerobic capacity, as much as 10 percent per decade beginning after age 25 to 30,” says Tracy Hafen, exercise physiologist and co-author of "The RealAge Workout." “Regular cardiorespiratory exercise, both moderate and high intensity, increases aerobic capacity by 20 to 30 percent, wiping out 20 to 30 years’ worth of aging effects.”