Muscles do not grow overnight. And neither on its own. You really have to do something for it. The fear of getting thick arms and broad shoulders overnight is unfounded. In my many years of experience, none of my clients have yet awoke one morning with sudden muscle growth. But: Muscles build up faster than the body fat. Be patient. If you start with strength training, you will build muscle faster than losing the same amount of body fat. You’re getting slimmer, but not necessarily lighter. My tip: Look more often in the mirror, not on the scales.