Apr 12, 20222 min read

How Long Can You Fast Without Losing Muscle? [Intermittent Fasting Tips]

How long can you fast without losing muscle? Today, we're diving into the details of how to incorporate your Intermittent Fast so that you can maintain muscle mass.

Can You Fast And Not Lose Muscle?

Is it even possible to fast without losing muscle? Absolutely! It comes down to two main factors:

how long you fast
how you break your fast

During a fast, the body turns on key muscle protecting hormones in order to prevent muscle breakdown. The main hormone that is elevated during a fast is called Growth Hormone.(1) When Growth Hormone is high, it protects the muscle from breaking down while also aiding in ramping up fat breakdown in the body. A win, win!

As one meta-analysis points out, Intermittent Fasting paired with strength training not only appears to maintain lean muscle mass -- it can even support muscle gain.(2) Another study taking a more critical stance of Intermittent Fasting found that when compared to standard calorie restriction, Intermittent Fasting appears to do a better job of preserving or even increasing lean muscle during a weight loss journey.(3)

Due to the fact that there are so many different ways to Intermittent Fast, there are certainly confounding variables. However one of the most important factors that nearly all researchers agree upon is that getting adequate protein to support muscle mass during the eating window is crucial. And this is where how long your Intermittent Fast is can come into play.

Curious how long YOUR fast should be for your goals? Take my free Intermittent Fasting Schedule Quiz by clicking the button below!

How Long Can You Fast Without Losing Muscle?

As noted above, Intermittent Fasting can help to preserve lean muscle by increasing growth hormone. However, if you don't get enough protein within your eating window to support muscle maintenance, then you can run into issues of muscle loss.

While Intermittent Fasting, you can have fasting lengths from 12 to 36 or more hours. Clearly, with fasts lasting longer than a day, you're not able to get all of your daily protein needs in. So if muscle maintenance is your chief concern, you'll want to aim for shorter daily intermittent fasts. (At this point, you'll definitely want to take my free Intermittent Fasting schedule quiz HERE!)

Because protein is the most satiating macronutrient, it can be a bit difficult to fit all of your daily protein needs in during a smaller eating window (with a longer daily fast). This is why the Complete Intermittent Fasting Bundle recipes focus on high quality sources of protein at each meal during the eating window.

From there, the length of time you fast each day depends on your own goals and needs. For example, if you're working on building muscle or if you have higher protein needs due to age related bone loss, then you might want to opt for a slightly shorter fast (12-14 hours). However, if your protein needs aren't as high, then you might do well with slightly longer fasts (16-20 hours).