Last Updated on April 12, 2024 by Fasting Planet
Each day, the foods you put into your system are specifically chosen to help you build and maintain muscle. Yet lately, you’ve considered going on a fast, so you wouldn’t be able to consume the proteins and healthy fats that have helped you reach this point. Can you continue or even start building muscle when on a fast?
It may be possible to build muscle when fasting depending on the type of fast you do and how you fuel your body during your eating periods. When you fast, your levels of human growth hormone increase, which can boost the muscle tissue in the body and theoretically lead to the development of more muscles.
Are you curious to learn more about building muscle on a fast? Then this is the article for you. In it, we’ll discuss whether fasting can cause muscle loss, what the data says about building muscle on a fast, and how to do it. Let’s get started!
Does Fasting Cause Muscle Loss?
Let’s start with a question we’re sure is on your mind. That is, when you fast, will you lose all the terrific muscle gains you’ve worked so hard to achieve? To answer that, let’s briefly cover what happens to your body during a fast.
When you’re not fasting, you get your energy through glycogen. This gets converted from glucose, a type of sugar the body makes and that you get in all the foods you consume. Some types of foods, such as carbs, have more glucose than others.
Each day, you wake up, eat, and fuel your body with glucose, which becomes glycogen through a conversion process. When your energy starts to flag in the afternoon, you eat again, giving yourself a pick-me-up. The same thing happens in the evening with dinner, and maybe a post-meal snack as well.
If your body has more glycogen than it necessarily needs at the time, it stockpiles it for a later date. The glycogen gets stored in the liver.
When you begin fasting, be it intermittently or a longer-term fast, you chip away at those glycogen reserves. Since you’re not putting more glucose in your system through food, your body has to use the glycogen it has, even that stored in the liver.
When the liver runs out of glycogen, since you’re not supplying more, your body turns to a new energy source: fat. In burning fat, your body will sometimes burn muscle proteins as well. This doesn’t happen at the same rate as fat burning by far.
According to a 2015 report in Nutrition Reviews, if you do lose muscle on a fast, it would take several months of intermittent fasting for it to happen. Even then, the lean mass lost is very insignificant, about two pounds.
Another study points towards the same conclusion as well. It’s from a classic report in Starvation as cited by Diet Doctor.
According to a writeup of the study, your brain will use ketone bodies for energy and your body fatty acids, both of which lessen the rate of gluconeogenesis. The study also notes that proteins break down at a rate of 15 to 20 grams each day of your fast. The Diet Doctor says that even if you were to lose up to 100 grams of protein through your fast then, when you resume regular eating again, you’d recoup the loss.
Can You Build Muscle While Fasting?
Now that you know you should be able to at least maintain muscle mass on a fast, or that you’ll lose very little muscle, let’s next talk about building muscle instead. This may seem difficult to do considering your body will sometimes burn muscle proteins when fasting.
Indeed, being on a fast is not the most ideal time to build muscle.
That’s because of how your body develops muscles. You know from reading this blog that to lose weight, you must eat fewer calories than you burn. That’s why it’s so easy to lose weight on a fast. Yet to build muscle, you need to consume more calories than your body burns. When you’re cutting your calories or you have only a small eating window as you do on a fast, getting all your calories in becomes tough.
Tough? Yes. But impossible? No.
The main reason it’s possible to build muscle on a fast is due to human growth hormone or HGH. Also known as somatotropin, HGH is a type of peptide hormone. It can cause your cells to regenerate or reproduce, and it leads to growth as well.
Your body has the most HGH when you’re an adolescent. Upon reaching adulthood, the levels drop. However, when you’re on a fast, your HGH goes up more than usual. This promotes healthier bone density, lessens body fat, and increases lean muscle mass.
In 2012, the journal Growth Hormone & IGF Research explored the relationship between growth hormone-binding protein (GHBP) levels and long-term fasting. GHBP acts as a growth hormone carrier protein, but there’s not a lot known about it outside of that.
During the study, the researchers tracked the participants’ GHBP levels three times a day. The study had 11 participants in all, four men and seven women. All were at a healthy, regular weight at the time of the study.
The researchers found that the level of growth hormone saw a spike when on fasts lasting at least 24 hours. The study concludes the following: “A 24-hour fast led to parallel increases in free and total GH levels whilst there was no discernible change in GHBP levels or the fraction of free GH. This suggests that GHBP plays a role in limiting variations of circulating free GH levels.”
Again, with not a lot known about GHBP, more research will be necessary to confirm these findings. What the study does say is that fasts of at least 24 hours boost growth hormone, which could potentially promote muscle building.
Longer-term fasts might be even more beneficial for this purpose, says a classic report in The Journal of Clinical Endocrinology & Metabolism. It may be possible to boost your HGH levels by five times the normal amount if you can extend your fasting window to 48 hours. This could allow you to recover from your workouts quickly while enjoying more muscle mass.
Not necessarily though.
A 2016 report in the European Journal of Sports Science shows that it’s not as easy to build muscle on a fast. The study involved 18 participants, all men. For eight weeks, they followed a specific training regimen. None were weight trainers.
The 18 men were split into two groups. The first group didn’t change how they ate, but they trained often. The second group did time-restricted eating, or intermittent fasting. For four days every week, they had an eating window of only four hours. Then, for the other 20 hours of those four days, they fasted. They too trained as often as the non-fasting group.
The first group, the ones that didn’t change their diet, had a strength boost and packed on five pounds of lean mass. The fasting group only maintained their muscle mass but did not gain any muscle.
How to Build Muscle on a Fast
To reiterate, the data above shows that while you can indeed build muscle mass on a fast, that fasting is not going to make it particularly easy to do so. Regardless, if you’re interested in proceeding with developing your muscles when in a fasted state, how you go about it is incredibly important.
The following methods may allow you to build muscle during your intermittent fast. At the very least, you’ll be able to maintain your muscle mass so you can focus on increasing muscle size between fasts.
Calorie Cycling
The first recommended method is what’s known as calorie cycling, which is also referred to as calorie shifting. As that name implies, when you cycle calories, you go from periods of consuming more calories and then periods of eating fewer calories. It’s not quite a form of intermittent fasting, and calorie cycling isn’t considered a diet.
That said, calorie cycling and intermittent fasting can indeed go hand in hand. You need to be on a type of intermittent fast that allows for greater eating windows to make the most of calorie cycling. For instance, the 16:8 fast–which calls for 16 hours of fasting and eight hours of eating–is a good pick.
The 12:12 diet, which is an even split between the hours spent fasting and the hours in which you can eat, is another option, as is the OMAD diet. This stands for one meal a day. That one meal has loose and very generous guidelines, so you can eat a whole day’s worth of calories at once or limit your consumption.
ShapeScale, a fitness tracking company, recommends calorie cycling when trying to build muscle on a fast. According to ShapeScale, you should focus on cycling more calories after you’re done exercising. Make sure you get lots of protein post-workout to keep your muscles healthy and big.
If you exercise every other day on an intermittent fast, you can cut back on the calories on those days you skip the workout.
How does calorie cycling help you grow bigger muscles? It’s simple. You’re much closer to abiding by the rules of building muscle, in that you must eat more calories than you burn. Do make sure you don’t go overboard on your calories though and that you’re sticking within the rules of your fast. Otherwise, you might build muscle, but you could gain a little extra weight as well.
Exercising
One of the keys to bigger muscles even on a fast is exercise. Some experts caution that you have to train at full capacity to work your way to more muscle mass. That said, when on a fast, even an intermittent one, you may find you have some symptoms that make high-intensity workouts difficult.
You could feel fatigued, hungry, and mentally fuzzy. All are normal side effects of severely limiting your calorie consumption, especially if you’re new to fasting. It’s generally not recommended to engage in high-intensity workouts on a fast because you could worsen the above symptoms and feel dizzy and weak due to the calorie deficit.
Try exercising as you feel comfortable and stop if you’re sick or woozy. Know that even if you can’t necessarily commit to the sweaty, heavy weightlifting workouts, you can still at least maintain muscle mass when fasting.
This 2017 report in Obesity (Silver Spring) suggests resistance training to keep muscles strong. Weight training with lighter weights is also recommended.
In 2016, the Journal of Translational Medicine did an eight-week study on a group of 34 men who were on intermittent fasts but also exercised. Half the men ate as usual while the other group had eight hours a day to eat.
The amount of protein and number of calories the men consumed didn’t differ between the two groups. What times the men ate did change though.
The men who didn’t switch their diet were able to maintain their strength and muscle mass. The same was true of the fasting group, but they also dropped 3.5 pounds of fat. Trimming fat can make muscles more apparent, which is almost as good as gaining muscle.
You can even ride an elliptical bike and keep your muscles in the same shape as in your pre-fasted state. That’s according to another study from Obesity (Silver Spring), this time in a 2013 report.
The participants in this study were on an alternate-day fast, which means they’d fast for 24 hours, then the next 24 hours, they could eat normally. Thrice every week, they rode an elliptical for up to 40 minutes. Their muscle mass didn’t decrease, but it didn’t increase either.
Supplementing
If you take supplements such as branched-chain amino acids or BCAAs, beta-alanine, protein supplements, or creatine, you may be able to continue doing so on an intermittent fast. Do be aware that many supplements contain calories, and some may have sugar that can create an insulin response.
Intermittent fasts that require you consume few if any calories, such as a water fast or a dry fast, would technically be broken if you take most supplements. If you’re on a 16:8 fast or OMAD diet though and you can consume calories for a window of time, then taking supplements shouldn’t pose a problem.
Conclusion
You can likely build muscle mass on a fast, but it’s not going to be easy. You may be better off focusing on maintaining your muscles while fasting and then spending non-fasting periods eating more calories to get buffer. Best of luck!