Everyone has heard that– “Be careful! If you gain too much muscle, when you stop working out it will turn into fat.”
Does anyone out there believe it? I hope not. Before we get into where this myth came from (There is a logical explanation for why this exists), let’s look at muscles and body fat.
Muscles are responsible for causing “force and motion,” and taking care of most internal functions. They’re composed primarily of water, and the fibers are made up of protein filaments. There are three types of muscles in your body: Cardiac, Smooth, and Skeletal; Skeletal muscle being what we’re talking about today.
Body fat, also known as “Adipose Tissue,” is your body’s storage system. Body fat is made up of fat cells (“Adipocytes”) that act as little compartments to store energy in the form of lipids. (It’s important to note that lipids include oils, waxes, fat soluble vitamins, but no water.) As you gain weight, your fat cells fill with lipids, and if you run out of available storage space, your body will create more fat cells. What is equal parts fascinating and terrifying is that your body can only create new fat cells; It has no natural way of getting rid of fat cells. Body fat is found beneath the skin (“Subcutaneous Body Fat”), around your internal organs, in bone marrow, and in breast tissue. Notice it’s not found within muscles.
So, we now have a slight idea of what muscle is, and what fat is. . . Now we can address this myth: “If you stop working out, your muscle will turn to fat.”
That’s impossible. At the risk of making a religious joke, unless you’re a deity, you cannot turn water into oil. Also, since these parts of your body are entirely separate, your body can’t simply transport muscle tissue into your fat cells and transform that into oil; Your body is not capable of such sorcery.
If your body isn’t capable of doing that, though, where did this myth come from?
From health nuts, bodybuilders, and fitness gurus retiring or taking a break. When you have more muscle than your body naturally wants, it takes a lot of work to maintain that muscle mass. If you stop weight training, you will slowly begin to lose that muscle– Your body will catabolize that muscle, breaking the tissue down into amino acids, which will then be used for energy. This is done for survival purposes. The human body is an incredibly smart and adaptable machine that will make sure it can survive; Muscle takes a lot more energy to maintain than fat, and if you don’t give your body a reason to maintain that muscle, it makes better survival sense to hold on to the tissue that doesn’t require as much maintenance.
So what happens while your body is breaking down the muscles? It’s in a fat sparing mode. While it’s creating energy from amino acids and dietary intake, it is not oxidizing fat for energy. So the amount of lean body mass goes down while the amount of fat stays the same– Thus, you will begin to look fattier.
There’s one more important part to this equation, though. Think of what is no longer happening to our hypothetical health nut, bodybuilder, or fitness guru. They’re no longer being active, and the chances are, if they’re giving up that lifestyle (or taking a break from it), they are no longer watching what they eat, or working out. So what does that do? It leads to gains in body fat.
So, with our hypothetical person, all of this is going on: Their body is sparing body fat while eating away muscle for energy, all while the subject is already gaining body fat.
It’s easy to see where the myth comes from, but just remember, it’s just that– A myth.