Gyms closing? Don't worry: Muscle doesn't "turn into fat" if you stop working out

40% of British gymgoers believe muscle turns into fat if you stop doing workouts, but it's not true

Woman lifting weights
(Image credit: John Arano (Unsplash))

With many gyms closing as a result of the ongoing global health crisis and the lockdowns in place, lots of us have to exercise at home instead. However, be careful when doing your fitness research at home: in the health and fitness community, bad and unscientific advice and untruths are rife. 

It's easy to see how popular gym myths propagate. If you've ever believed a cardio session under 20 minutes isn't worth doing, or it's not been a good workout if you're not sore the next day, you're not alone: all these are common fitness misconceptions.   

Another common untruth is the idea muscle will "turn into fat" if you stop exercising. According to a poll of 2,486 gymgoers collected by MyVitalMetrics, a London outfit conducting science-based body-composition assessments, 40% of the participants believed muscle actually turns into fat if you stop exercising. 

This is untrue: fat cells are very different from muscle on every level, from makeup to function. Where the myth seems to come from is that when you stop training your muscles to become stronger, they undergo a process known as atrophy, or muscle wastage. If the muscle is not needed, it will shrink, as it is no longer undergoing the strains of tearing and healing it requires to get stronger. 

Bench press

(Image credit: iStock)

In addition, when you stop exercising, you are of course expending fewer calories. The International Journal of Obesity shows us the relationship between energy intake and energy expenditure is directly related to obesity. If you're expending less energy, you have to reduce your food intake to avoid gaining weight.

Of course, this is more difficult than it sounds. The American Journal of Clinical Nutrition found high-intensity exercise increases your appetite. If you simply stop working out, you might be so used to eating more to fuel your body that your increased appetite remains, even when you're not expending very much energy. 

The end result is more excess energy being stored as fat. Therefore, while muscle doesn't necessarily turn into fat per say, your muscles do shrink, and people do tend to accumulate fat instead, when you stop exercising. It's easy to see how the myth became so commonplace.  

Swiss ball

(Image credit: Getty)

Of course, if you want to maintain your muscle gains over lockdown, you can rely on bodyweight training. You won't be able to overload your muscles with progressive weights if you're a serious lifter, but most of us can use variations on push ups, pull ups, squats and other bodyweight exercises to continue to build muscle. 

It's not just the myth above that's widely believed: a huge 64% of study participants believed you should work out every day, despite the fact rest days are very important. Another 45% believed you should do at least 20 minutes of cardio to make it worthwhile, when studies show even short runs help you live longer.  

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Matt Evans

Matt Evans is an experienced health and fitness journalist and is currently Fitness and Wellbeing Editor at TechRadar, covering all things exercise and nutrition on Fit&Well's tech-focused sister site. Matt originally discovered exercise through martial arts: he holds a black belt in Karate and remains a keen runner, gym-goer, and infrequent yogi. His top fitness tip? Stretch.