I am going to write this article just so that this myth is eliminated. Does fat turn into muscle? Simply, no.
Muscle is made up of many different things including protein and mostly water. Fat is made up of various substances as well, however they are completely different than the substances that make up muscle. In order to build more muscle mass, one very important thing must happen generally: You must be in a caloric surplus. This means that you must be consuming more calories than you burn by both metabolism and activity. This must happen because adding muscle is adding mass, and you can’t just create mass out of thin air.
On the other hand, in order to burn fat you must be in a caloric deficit. This means that you must burn, by metabolism and activity, more calories than you consume. This is required because your body needs to get the energy to survive and function from somewhere, and if you are not taking in enough calories to meet its needs, it must take the calories from somewhere (read: fat cells). Now, it should be noted that fat is not the only source of energy for your body. In fact, in many cases your body would like to keep as much fat as it can because it does not take a lot of energy to keep around. In other words, it’s not very metabolically active. Muscle, though, is very metabolically active (that’s why the more muscle you have, the higher your metabolism will be). So your body would love to take the energy it needs from your muscles in the form of protein (the protein is converted to glucose for energy) and from your glycogen storages. However, this is beyond the scope of this article.
All in all, muscle and fat are two very different things and cannot just be converted into one another. In some somewhat rare cases, someone can start lifting weights with a caloric surplus, gain some muscle which, in turn, raises the person’s metabolism so that if that person eats roughly the same amount of food everyday, they will start to lose fat. Ta-da! Fat seemingly turned into muscle.