Fact: You'll often hear someone at the gym say something like, "Since my injury, my muscles have turned to mush." But this isn't the case because muscle and fat tissues are entirely different, and therefore they can never transform from one to the other. It's the equivalent of saying you can turn water into wine or lead into gold.
What really happens when you stop exercising is that your muscle mass declines. And how you gain fat tissue is when you eat more calories than you burn off, which is much easier to do when you're not exercising. And likewise, when you up your exercise routine, you'll add lean tissue and might start burning excess body fat, but your fat didn't turn into muscle.
