Intermittent fasting is good for a lot of things—brain function, weight loss, inflammation, longevity. Those all get a lot of attention, but there’s also a lesser-known benefit of fasting that you don’t hear about as often: intermittent fasting is a great way to build muscle. 

It’s counterintuitive: you’d think skipping meals would make you lose muscle, not gain it. But a growing body of research shows that fasting can help you maintain and increase muscle mass, even as you lose weight—and thanks to a new study, we’re starting to understand why. 

Here’s a look at the latest research on fasting and muscle gain, and how you can use intermittent fasting to see better results in the gym. 

Intermittent Fasting Helps You Build Muscle and Lose Fat

Over the past decade or so, research has found that intermittent fasting is good for muscle growth. Here’s a snapshot of a few studies:

  • In a 2019 study, women did 16:8 fasting (fasting 16 hours a day, then eating all your food in an 8-hour window) paired with weightlifting for eight weeks. The women who fasted gained an average of one pound more muscle than women who followed the same protocol, but spread their food out across the day instead of fasting. 
  • In a 2016 study, men did strength training for eight weeks, paired with either all-day eating or 16:8 fasting. The contents of both groups’ diets were identical; the only difference was the timing. The men who fasted gained the same amount of muscle, but lost significantly more fat than the men who ate throughout the day. 
  • In a 2018 study, overweight adults combined exercise with either alternate day fasting (eating every other day) or normal eating. The alternate day fasting group maintained the same muscle mass, but lost almost twice as much fat as the group that ate normally. 

In all of the above studies, people who fasted either gained muscle or maintained muscle while losing fat, and in each case, the fasting group outperformed the normal eating group. 

Why Is Fasting So Good for Muscle Growth?

It’s worth mentioning that gaining muscle while losing fat is unusual. Typically you lose a small amount of muscle as you lose fat. 

But studies have shown, over and over, that fasting helps you maintain (or build) muscle, even as you get leaner. It clearly happens, but until now, researchers haven’t figured out why. 

I say “until now” because a new study, published just a couple weeks ago, has shed some light on why fasting is so good at preserving and building muscle. 

The study was done in fruit flies, which may sound odd at first. It turns out, however, that fruit flies are one of the best (and most widely used) ways to study genetics. They share a lot of genes with humans, and the results of fruit fly studies usually translate well to human research. 

In this recent paper, researchers took obese fruit flies and put them on an intermittent fasting protocol. Then they studied the flies’ DNA, trying to figure out how fasting affects gene expression. 

The researchers found a few interesting things:

  • Fasting turned up the volume on genes that control glycine production and use. Glycine is an amino acid that’s essential for building muscle. 
  • Fasting turned off genes that break down muscle and drive age-related muscle loss. 
  • Fasting made the purine cycle more efficient. The purine cycle controls how much energy your muscles need to function. When the purine cycle runs more efficiently, your muscles can work harder for less energy, which increases your endurance and can help you build more muscle over time. 

Basically, when overweight fruit flies were put on a fasting diet, their genetics changed toward building and keeping muscle. 

We can’t be sure the same thing is happening in people, of course. While fruit flies are surprisingly similar to us genetically, they are decidedly not human. 

However, the results of this study line up nicely with all the human research on fasting and muscle building. Flies who fast are genetically primed to build and keep muscle; humans who fast become better at building and keeping muscle. The parallels are pretty cool to see. 

Use This Fasting Protocol for Faster Muscle Gain

If you want to use intermittent fasting to get into better shape, you’re in luck. Fasting is easy to do; all you need is some basic knowledge about how to fast and what to expect. 

My Beginner’s Guide to Fasting is free and has all the information you need to start fasting today. You can pair it with your current exercise routine and get the full benefits of fasting for muscle gain. 

And if you want more personalized fasting guidance, as well as the support of a vibrant community, the chance to drink coffee and chat with me on a regular basis, and weekly group workouts (usually set to my favorite ‘80s hits), consider joining the Reset Academy. We have a lot of fun getting healthy together, and the group support makes a world of difference.