Does muscle weigh more than fat? One pound of muscle and one pound of fat weigh the same: one pound. The difference is the amount of space they both take up. Like we mentioned above, one cubic inch of muscle weighs more than one cubic inch of fat. But, why? We’ll answer that in the next question. Muscle vs. fat density: Which one is more dense? Why does muscle weigh more than fat? It all has to do with density and overall composition. Muscles are made of long fibers tightly woven together. Fat, on the other hand, is composed of different sized droplets and some are more full than others. These droplets stick to each other but leave some empty space in between. In the image below, you’ll notice that one pound of muscle takes up less space than one pound of fat. This is why you might notice a slimmer waistline but no drastic change on the scale as you begin a new workout or meal plan regime – your body is burning light fat, but building heavier muscles.