toned muscles. Research shows that between the ages of 30 and 50, you're likely to lose 10 percent of the total muscle on your body. And that percentage will double by the time you're 60! Worst yet, that lost muscle is likely to be replaced by fat over time. According to a study done by The American Journal of Clinical Nutrition, scientists there found that even people who maintained their body weights for up to 38 years, lost 3 pounds of muscle and added 3 pounds of fat per decade. Not only does that make you look flabby, it increases your waist size. That's because 1 pound of fat takes up 18 percent more space on your body than 1 pound of muscle. So keep pushing those weights and you'll look great!