Do Muscles Really Turn to Fat When You Stop Working Out ?

A lot of people are saying this phrase nowadays: “I used to be athletic and had muscles before, but ever since I stopped exercising it turned into fat”. Does this sound familiar to you?

When you think about it, it doesn’t seem like it makes sense at all, the notion that muscle can be turned into fat, but we’ve all seen athletes from various sports turn into fat slobs after their career has ended. Sometimes, they get really obese. So, even though the notion that muscle tissue turns into fat doesn’t make sense, without any reasonable explanation, anyone can start believing this or even deem it logical for a lack of a better answer.

It’s time to put a rest to this myth once and for all:

Muscle DOES NOT turn into fat. It is impossible.

There’s no such process inside the human body through which muscle tissue, which is mainly comprised of protein, amino acid, and water, turns into fat (adipose) tissue, which is primarily made up of adipocytes. Our bodies, regardless of the things that they’re sometimes able to do, can’t magically transform one type of tissue into another.

If that’s not the case, then what is actually going on? What happens is a negative change in the body’s tissue composition. To be more specific, it is a loss of skeletal muscle mass in combination with fat mass gain happening at approximately the same rate and the same time. Let’s delve into how this happens and what can be done to avoid it.

Muscle loss

Even though you may not be aware of it, but you lose muscle every minute of your life. This is because the muscles, the same as with any other type of tissue in your body, depends on the balance between the formation of new cells and dying out of old cells (cell turnover) and protein synthesis. That means that the body is constantly breaking down the protein inside the muscle tissue and then constantly rebuilding it. You actually want the body to do is, it is a part of the continual process of keeping you alive.

Skeletal muscle tissue grows and develops via proper nutrition, which includes proper amounts of protein which provide the muscles with the necessary amino acids, as well as exposing them to mechanical stress (exercise). The inverse process is: when you become less active physically and your nutrition no longer satisfies the demands of the increased muscle mass, your body will enter into a catabolic (tissue breakdown) state, known as muscular atrophy.

Muscles which are used only partially, using less than twenty percent of their maximal capability, will start to atrophy after a while. Not using them completely is a lot worse; muscles that aren’t used at all, for example, when someone is bedridden and is unable to move at all or only a little, can atrophy at a rate of 1/8 of their total strength a week.

But, if you aren’t suffering from any serious health complications, your muscles will not atrophy at such a drastic rate as someone who is unable to move or is forced to move very little. However, if you were already very physically active before and your body was used to intense training and you suddenly stop, the body will see no reason to maintain your current muscle mass and will begin to degrade.

Your muscles do not transform into another type of tissue, instead, they start to disappear and are instead replaced with something else. Here’s how it occurs.

The same diet with a different lifestyle

Now, let’s explore the second part of this false claim: if the muscle doesn’t turn into fat, then where does the fat come from?  Since we’ve already explained that muscle tissue is broken down, not turning into something else, then logically one concludes that the newly appeared fat had to come from somewhere.

The answer is that fat always accumulates because of one reason only: an energy surplus, which is caused by consuming more calories than you’re actually burning. Even though for the majority of people this isn’t news, it can sometimes surprise people, especially those who are used to being fit and athletic.

Athletes need great amounts of energy in order to excel at their sport. Their bodies require a great amount of all the macro-nutrients to keep their body supplied with energy at all times. To get all that energy, they need to eat huge amounts of food, the ones that an average person would normally eat in 3 or 4 days. For example, NFL quarterbacks have been reported to eat somewhere around 4000-6000 calories a day, evenly spread out over a 6-7 meal a day, in order to be in a peak physical condition.

One big reason why these high-performance athletes such as NFL quarterbacks need such a big number of calories is that they usually have a higher-than-average quantity of lean body mass compared to average people at the same height. This is important because as lean body mass increases, the basal metabolic rate (BMR) also increases. BMR is the number of calories your body needs while resting, without the calories required for digesting food and movement.

It’s worth noting that the BMR is not the total number of calories you need daily. A more accurate way to calculate the number of calories you need per day is the total daily energy expenditure (TDEE) parameter, of which BMR forms just one part. If you want to calculate the TDEE, you will first need to calculate the BMR and they multiply it by a factor which is determined by your level of physical activity.

Professional football players, for example, would be under the “extremely active” category as their full-time job involves strenuous amounts of high physical activity. It’s important to take note of the fact that this number is actually the number of calories that this person needs to eat in order to maintain his current weight because of his/her lean body mass and more importantly at his current physical activity level.

Now, what would happen if this same person stopped being active or greatly reduced their training and took a 9-to-5 office job, jobs which usually involve sitting most of the time? The TDEE would quickly plummet since the physical activity level would decrease significantly.

In order to counter this, this individual would have to adjust his diet regimen accordingly and consume fewer calories than he did when he was more active. The problem here is that people usually become accustomed to consuming a certain amount of food during the day, especially when they’ve lived this way for prolonged periods of time. They kind of develop a vague mental understanding of the amount of food they can eat, and they very often cook and/or order meal sizes that match this understanding they have in their head of how much food they think they need.

When you increase/decrease your level of physical activity, you also need to increase/decrease your caloric intake. So, if one who has continued to eat the same amounts of food as he did when he was extremely active, they would find themselves in a huge caloric surplus, which means lots of unnecessary calories per day, which in turn would inevitably lead to fat gain. Doing this for an extended period of time would lead to accumulation of fat tissue which could pose a serious risk to one’s health.

Who is at risk and what can be done?

So, let’s recap. We have already concluded that muscle cannot be turned into fat. Looking at it from a body composition aspect, here’s exactly what’s happening:

A decrease in skeletal muscle mass leads to a decreased lean body mass.

Skeletal muscle mass is decreased because of not using it. The basal metabolic rate is decreased accordingly.

Since activity level has decreased, total daily energy expenditure has decreased as well.

Intake of energy stays the same, despite the decrease of TDEE. This leads to a caloric surplus.

Caloric surplus, in turn, leads to the accumulation of fat tissue.

People who have a tendency to accumulate a greater amount of fat are, in a somewhat ironic twist, the same people who are at their peak physical condition right now. This is because when you’re at a peak condition, it’s likely that you’re at an optimal nutrient/caloric intake matched with a level of training which allows you to achieve your physique goals, which ultimately means you are in balance.

But, if you ever decrease your level of physical activity, your diet must be adjusted accordingly or you may start eating a caloric surplus. That adjustment may be more than you would expect and you would have to make some sacrifices. Another fix is to find some new ways to increase your physical activity which best suits your lifestyle. Even though you might not be able to perform at high intensity every day, you can find other ways to be active and do it based on a schedule that best works for you.

And finally, you should measure your body composition on a regular basis so that you always be vigilant about the condition in which your body is and make sure that you are maintaining the level you want to be at. When testing the body composition, you’ll be able to track your lean muscle mass and fat mass and check whether they’re increasing or decreasing. Having that information will help you determine if you need to take action and make some changes to ensure that you stay as healthy and fit as possible.