As you can see in this picture, the 250 lbs. of fat is much bulkier than the 250 lbs. of muscle… A 250 pound pile of fat will take up more space (volume) than a 250 pound pile of muscle. A woman weighing 150 pounds with 19% fat will look much smaller (and be much healthier) than a woman at 150 pounds with 35% fat. They weigh the same, yet the composition is different. Because muscle is denser than fat, the person with less fat and more muscle will look smaller. Once you understand this, you will stop being so concerned with body weight and start paying attention to body composition. How much body fat do you have compared to muscle?
If you want to look slimmer, the key is to build more muscle and to burn more fat! And remember, when it comes to fat loss, exercise is the method that can be most easily manipulated… the more active you are, the more fat that you will burn!