Bodybuilding legend Arnold Schwarzenegger is clearing the air about one of fitness’s most popular myths. On Nov. 18, 2025, he took to his Arnold’s Pump Club Newsletter to reveal whether muscle turns into fat after time away from training.
Having conquered the Mr. Olympia stage seven times throughout his career, Schwarzenegger forever etched his name into bodybuilding history. While he hasn’t competed in years, he’s still a passionate bodybuilder, having worked tirelessly to preserve his longevity and muscle tissue at 78 years old.
Fat doesn’t melt off his body like it once did, leaving “The Austrian Oak” seeking proven methods for staying in shape. Although he has taken time off training before, Schwarzenegger is adamant that it hasn’t stopped him from maintaining his lean muscle.
Arnold Schwarzenegger Discusses If Muscle Turns Into Fat
In the newsletter, Schwarzenegger explained what really happens to muscle when lifters stop working out. Despite some suggesting that it will turn muscle into fat, he said that’s far from the truth.
“Friends Don’t Let Friends: Believe That Muscle Turns Into Fat (Here’s What Really Happens)
If you’ve ever looked in the mirror after a little too much time away from the gym and thought, “My muscle turned into fat,” you’re not alone. It’s one of the most common fitness myths, but biology tells a very different story.”
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Schwarzenegger broke down the difference between fat cells and muscle fibers, noting that they cannot ‘transform into each other.’
“Muscle and fat are completely different tissues, and one can’t magically transform into the other.
Your muscle fibers (myocytes) and fat cells (adipocytes) are built from entirely distinct cell types. Under normal conditions, they cannot convert into each other, just like your bones can’t turn into skin. Scientists have confirmed this in cellular biology studies showing that even muscle stem cells exposed to extreme conditions don’t become fat cells.”
The reason it appears that the muscle turns to fat after not training is twofold: muscle atrophy and fat accumulation.
“So why does it look like your muscle is turning into fat when you stop working out? Two separate processes happen at once:
Muscle atrophy: Without resistance training, your muscles shrink and lose tone.
Fat accumulation: If you keep eating the same amount while burning fewer calories, your body stores the extra energy as fat.”
Additionally, Schwarzenegger explained that some fat from the muscle only exists because separate cells in that tissue expand with inactivity or aging.
“These changes happen simultaneously, creating the illusion that muscle turned into fat. But it’s just that — an illusion.
Some fat may also appear within the muscle (called intramuscular adipose tissue), but it doesn’t come from muscle fibers transforming. It forms from separate cells that already exist in muscle tissue and expand during inactivity or aging.”
The bodybuilding icon emphasized that both muscle atrophy and fat accumulation are reversible:
“The best part? Both processes are reversible. Retraining helps you regain lost muscle faster than when you first built it. And adjusting your calorie intake during breaks can prevent most of the fat gain in the first place.
Your muscle isn’t vanishing into fat, it’s just waiting for a signal to come back stronger,” Arnold Schwarzenegger shared.
Schwarzenegger believes quality muscle is the currency of health. He recently broke down how building muscle can help individuals burn fat and control blood sugar. Even though cardio is often seen as the most optimal weight loss method, he contends that resistance training sets the table for long-lasting gains.
If you’re worried that your muscles will shrink after skipping a few workouts, Schwarzenegger said to rest easy. He emphasized that those muscle cells are ready to bounce back as soon as you get back in a groove.
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Well explained. Muscle never actually turns into fat – people just lose muscle and gain fast when they stop training.
I also share simple fitness tips and diet guides on my blog: fitnessinfromation.in