The 11 Biggest Fitness Myths Trainers Wish You Would Stop Believing

Just like how fat doesn't magically turn into muscle, muscle won't turn into fat if it's not used.

"Anybody who has ever broken a bone and had a cast knows that when we stop using certain muscles, they atrophy, but our fat-storing process exists independently and is our body's way of conserving energy for future use," Rob Sulaver, CSCS, founding trainer of Rumble Boxing, told POPSUGAR. "Muscles can shrink if they're not used, and fat can be gained or lost depending on our energy surplus or deficit."

So if your six-pack abs give way to a full keg, your ab muscles haven't all of a sudden become fat; fat and muscle are two totally separate entities.