This is a great visual of fat and muscle!
Notice how although both are the same weight, the muscle is much smaller? That’s because muscle is denser than fat. Muscle is also metabolically active tissue.
Metabolic rate is determined by the amount of fat-free mass in your body. Fat-free Mass (FFM) is made up of internal organs, muscle, and bone. So basically, the more muscle you have, the higher your metabolic rate will be. That’s one of the reasons why weight training is very important to overall fat-reduction. A higher metabolic rate = more calories burned, which makes it easier to lose body fat! (That’s a simplified explanation, but you get the idea!). =)