Does muscle turn to fat? Arnold Schwarzenegger busts another fitness myth!

I'm sure you've heard it before. Maybe your grandmother or a friend who "used to exercise too" scared you. The phrase goes something like this:

"Don't overdo it with the exercise, because once you stop, all those muscles will turn to lard."

It's one of the most common fears that discourages people from building muscle. But is there any truth to it? The legendary Arnold Schwarzenegger recently decided to bury this age-old myth once and for all in his newsletter , Arnold's Pump Club.

"Friends don't let friends believe nonsense."

Arnold, who remains an active promoter of fitness and healthy living even at 78, is clear on the matter. In a recent post, he explained that biologically, converting muscle into fat is complete nonsense.

"If you've ever looked in the mirror after a long break from the gym and thought, 'My muscles have turned to fat,' you're not alone. It's one of the most pervasive fitness myths, but biology tells a different story," writes Arnold.

Why is this biologically impossible?

Schwarzenegger explains that muscle and fat are two completely different tissues. It's like mixing apples and pears - one can't magically turn into the other.

• Muscle fibers (myocytes) and fat cells (adipocytes) are built from completely different cell types.
• They can't normally turn into each other, just like your bones can't turn into skin.

Scientific studies confirm that even muscle stem cells exposed to extreme conditions do not turn into fat cells.

So where does the illusion come from?

If it's not true, why does it so often seem that former athletes "melt" into fat? Arnold explains that behind this optical illusion are two separate processes happening simultaneously:

1. Muscle atrophy: When you stop working out (remove the stimulus), the muscles shrink and lose their tone. The body sheds tissue it doesn't "need" because it is energy-intensive to maintain.
2. Fat accumulation: If you stop exercising but still eat the same amount of food as you did during your workout, you suddenly have a huge calorie surplus. The body stores this extra energy as fat.

The result? You have less muscle under your skin, but more fat. It looks like a trade-off, but it's actually the confluence of losing one and gaining the other.

Good news at the end

However, Arnold doesn't just stop at busting myths, he adds a positive outlook. Both of these processes are reversible.

• Muscle memory: thanks to the myonuclei (nuclei in muscle cells) you've gained through training, it's much easier to regain muscle than to build it back up the first time.
• Fat Control: By adjusting your diet when you're not exercising (reducing calories), you can prevent fat accumulation altogether.

The lesson according to Arnold: Your muscles aren't going anywhere, nor are they turning to jelly. They're just waiting for a signal to come back stronger. So don't be afraid to lift heavy weights - they won't turn you into fat.