How Long Does It Take to Lose Muscle?

 December 8, 2023|  Dona Maria

Unlike belly fat which never seems to go away, it is often thought that if you don’t use your muscle mass, you lose it. While this is partly true, it’s a little more complicated than that.

Whether you’re coming off an injury or a long break from the gym, you’re probably wondering how much damage your rest period has done to your gains. So, here’s everything we know about maintaining lean tissue.

Is it possible to lose muscle?

You can ultimately lose any type of body weight including fluid, fatty tissue, and muscle – especially when cutting calories. However, your body tends to prefer burning fat over muscle when it needs the fuel.

Lean tissue is what our bodies use to store nutrients, provide strength to our frame, and power our metabolism which is why your body tends to want to hang on to it as much as possible.

Muscle Atrophy, Malnutrition & Low Protein

Muscle atrophy caused by age

Unlike fat which requires a calorie deficit to lose, muscle loss can be achieved with inactivity alone – through muscle atrophy. This can also occur naturally as you age, and as a result of malnutrition or an incredibly low protein intake.

How quickly muscle atrophy happens will depends on your current fitness level and the amount of time you were inactive. The more muscle mass you have, the harder it is to maintain with inactivity and the more you’ll potentially lose. In other words, fit individuals are likely to lose muscle mass more quickly than unfit individuals.

How long does it take to lose muscle?

Woman being inactive in bed

Some research suggests that you can start to lose muscle in as quickly as one week of inactivity and another study suggests your muscle size can decrease by about 11% after ten days without exercise, even when you aren’t bed ridden.

But don’t panic. There’s no need to regret every vacation or week off you’ve taken, it is important to understand that true muscle atrophy typically takes place during times of injury or when you completely stop using your muscles for an extended period of time – having your leg immobilized for two weeks or more is different from taking a couple weeks off from weight lifting.

Additionally, a decrease in muscle size doesn’t always mean muscle loss. It could be a decrease in fluids. When you take a break from training, water loss and glycogen depletion can cause your muscles to decrease in size by up to 20% in a week.

The after workout “pump” you’ve learned to love so much is directly tied to this and your glycogen and water store can return fairly quickly once you start exercising again.

Does muscle become fat?

Man's body composition changing due to inactivity


Muscle and fat are two entirely different types of cells and they often require different nutrition and methods to increase or decrease.

The longer you take time off, the more your body composition begins to change. Muscle cells will shrink and your fat cells can expand, making you feel less toned but it doesn’t mean your muscle is turning into fat – especially if you are eating the right amount. If, however, you are eating more calories than you need, you will gain fat alongside your muscle loss.

The easiest way to tell if you are losing muscle is through a body composition test. Outside of this, pay attention to your strength, physical measurements, and body weight to help indicate any muscle loss.

How long does it take to regain muscle?

Regaining muscle mass by going to the gym

If you stop training and muscle atrophy occurs, it is entirely possible to regain what you’ve lost. Thanks to muscle memory, it can happen faster than it took to gain that muscle the first time around.

There is no exact answer for how fast this can happen; some research suggests that it’ll take you three times the amount of time you were inactive to regain the muscle mass that you’ve lost if you were fully immobilized. But this time-frame can depend on the person and whether or not you’ve been using your muscle at all.

If you can’t hit the gym and are worried about losing muscle mass or looking to regain the muscle mass you’ve already lost, here are three sure fire ways to help protect your lean tissue:

1. Maintain Your Calorie Intake

Weight loss of any kind occurs from decreased calorie intake while eating too much while inactive can lead to excess fat gain. One of the most crucial approaches to keeping your gains and maintaining your body composition is getting the right amount of calories each day.

2. Use Your Muscles

Heavy lifting can support muscle strength but isn’t required to build muscle. All you really need to do is use them on a consistent basis. This includes any type of strength training or resistance training (bodyweight movements, exercise bands, etc.), even if only a few times a week, can help protect your lean mass.

3. Eat Plenty of Protein

Muscles are made up of protein, and if your body isn’t getting enough protein through diet, your muscles are some of the first places you body will steal protein from to support your nutrition needs. So, making sure you’re eating a high protein diet is crucial.

In fact, research even suggests that higher protein intake can help maintain your muscle in a calorie deficit, while you lose body fat instead.

Support your muscle building with a nutritionist approved, science backed meal plan from Fuel-Up. Build your meal prep to support your personal goals with the help of one of our experts.

 December 8, 2023 | Dona Maria
Dona Maria

About the Author

Dona Maria Mesmar is the Nutrition Manager for Kcal Brands. She develops nutrition and diet programs for athletes and provides them with one on one nutrition consultation to help them achieve their body composition goals. She is also a certified fitness instructor, published nutrition writer and has appeared numerous times on national live TV, where she has provided expert advice on nutrition and healthy eating.

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