You probably don't need scientists to tell you that your metabolism slows with age. But they're studying it anyway-and coming up with exciting new research to help rev it up again. The average woman gains 1 1/2 pounds a year during her adult life — enough to pack on 40-plus pounds by her 50s, if she doesn't combat the roller coaster of hormones, muscle loss, and stress that conspires to slow her fat-burning engine. But midlife weight gain isn't inevitable: We've found an exercise and diet plan that will tackle these changes.

Prevention's customizable metabolism-boosting workout will help you shed up to 8 pounds in just 4 weeks. Most important, you'll build firm, lean muscle tissue — the key to a robust metabolism. But that's just the beginning. To really make your metabolism soar, couple the workout with our High-Metabolism Diet, developed by Dan Benardot, PhD, RD, an associate professor of nutrition and kinesiology at Georgia State University, and Tammy Lakatos, RD, co-author of "Fire Up Your Metabolism." Start today and you'll sleep better, have more energy, feel firmer, and notice your clothes are looser in as little as two weeks. Click on the arrows above to learn how.