Yes, you lose weight when you cut calories, but pounds lost aren’t always fat. Some of your weight loss may also come from muscle tissue. Cyclists that diet often end up thinner, but risk becoming slower and weaker on the bike. As pioneering diet expert Covert Bailey once wrote, “When someone says that they lost 20 pounds, the key question is: 20 pounds of what?” Some dieters can end up having a higher percentage of body fat even as they lose weight. And don’t forget that muscle burns calories. The more muscle volume you have, the more calories your body can burn—even when you’re just lying on the couch.