If you’re into fitness and trying to lose weight I’m sure you’ve heard of plenty different fasting diets.

Intermittent fasting is one that has an eat-stop-eat approach where you fast for 24 hours once or twice a week.

How impactful is it for weight loss and can you still maintain muscle while doing so?

Will You Lose Muscle If You Don’t Eat For 24 Hours?

No, it takes about 3 weeks of not training for your body to start using protein as fuel. However, the body cannot gain new muscle mass, recover properly from workouts, and provide you enough energy in the gym if you are fasting. While you will not lose your muscle, it will be hard to build new muscle.

How Long Does It Take To Lose Muscle?

It takes about three weeks of inactivity for your body to start losing muscle. As long as you are eating some protein and doing some kind of endurance training you muscle will stay.

So one day of not eating will not hurt your gains.

Muscle atrophy is the process of muscle breaking down. It occurs when we age and if we are malnourished or are not eating enough protein.

The more muscle mass that you have on your frame, the quicker you will lose it with inactivity. This means that fit people will lose muscle quicker than unfit people if they are not training.

Will You Lose Muscle If You Don't Eat For A Day?

What Happens To Your Body When It Has No Food?

Once the body hasn’t had any food for eight to twelve hours, your glucose storages become depleted. Glucose is the form of carbs that your body uses as energy.

Once it runs out of carbs to use, the body starts to burn amino acids to provide energy. Your body will then start to turn to fat stores for energy, and lastly protein.

Protein and muscle stores wouldn’t be used until about day three of not eating. Also, the more body fat a person has, the more that will be burned before protein is touched.

So, someone who is overweight would hold onto muscle longer than a leaner person would.

Note that while the body can maintain muscle while doing 24 hour fasts, it is very difficult to build any new muscle. This is because you won’t able to go as hard in the gym due to having no energy on fasting days.

You can combat this be only training on non fasted days. Your muscles will struggle to grow though as they are receiving no protein on fasting days. They also won’t be able to recovery properly.

If you goal is muscle growth, you may want to try a different type of intermittent fasting such as the time-restricted eating or periodic fasting.

Intermittent Fasting Eat-Stop-Eat Approach

Not eating for 24 hours at a time is a part of intermittent fasting known as the eat-stop-eat approach. During this time period, only calorie-free beverages can be consumed. These include water, diet soda, coffee and green teas.

Intermittent fasting has proven to have positive effects on weight loss, metabolism, and cardiovascular health. People believe that it is safe to do once or twice a week even to achieve results.

Don’t get too excited though, going an entire day without any food is extremely difficult and requires a lot of discipline. Think of how hungry you get when you go 5 or 6 hours without eating. Now try to imagine a full day.

There are of course many ways to make this easier such as drinking plenty of water and caffeine, but it’s still no walk in the park and definitely isn’t for everyone.

Consider contacting your doctor to see if fasting is right for you, as it can be dangerous to some.

Eight hours into your fast the body will still be digesting your last intake of food. Your body will use the stored glucose as energy.

After the eight hour point your body will begin to use stored fat as energy. This process will continue throughout the 24-hour period. Any fasts lasting longer than 24 hours and your body will start to dip into protein stores to use energy. This is when muscle is lost.

So as long as your fast doesn’t exceed the 24-hour mark, you can be sure that you aren’t losing muscle.

There doesn’t seem to be any restrictions on what people can eat on their non-fasting days. They should steer away from low carb diets as this will make them have very little energy, especially when they are fasting on certain days.

They should also avoid overeating as this can undo the effects of the fast.

Note that no exercise or training should be done on fasting days as you will be too weak and not have enough energy to complete a full workout.

However, going for a walk or doing activities that keep you busy will help you not think about your hunger as much.

Benefits Of Fasting

Since you are eating a lot fewer calories, you will lose weight. Fasting helps the body break down cholesterol and sugar which reduces the risk of diabetes and cardiovascular disease.

Fasting is quite an easy method to follow, especially compared to some diets where you can only eat certain types of food. You simply choose a 24-hour period and do not consume any calories.

Days when you are not fasting you are free to eat as you please, while obviously not overdoing it.

There are a lot of studies and experiments proving that intermittent fasting does help with weight loss.

Intermittent fasting diets have also shown to improve leptin, adiponectin, and c-reactive protein which are markers of inflammation.

It has also been proven to lower blood pressure and cholesterol levels.

When not eating for long periods of time, your body starts burning fat as fuel instead of carbs or glycogen. Instead of storing fat on your body, it will burn it. This is the state of ketosis that is focused on in keto diets.

If you’re looking for a way to promote fat loss on your body without fasting, see here.

How To Break Your Fast Properly

Yes, you can do this incorrectly. After not eating for 24 hours, it’s very easy to stuff your face with everything in sight. This is not safe or healthy.

Start with a small meal and chew each bite thoroughly and slowly. This ensures that you do not strain the digestive system. You should also eat easy digesting foods such as cooked vegetables rather than raw ones.


If you are starving every day that you fast and it’s causing you to be extra cranky and you have no energy to get anything done, it’s probably not worth it.

Those who work physically demanding jobs will not want to fast. Your body needs carbs to give you energy throughout the day to perform tasks.

Many people can get headaches, dizziness, and nausea from not eating. Note that this type of approach is not suitable for diabetics, pregnant women, or those with eating disorders.

Many people may be so hungry that they go on unhealthy binges and eat whatever they want the day prior to their fast. This is obviously not ideal and will ruin all of your hard work that you just did.

If you have serious side effects and can’t maintain fasting, then you probably shouldn’t be doing it. Listen to your body and see what feels right for you.

Leave any questions or comments below and I’ll get back to you!

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