Benefits of Strength Training on a Water Fast - Fasted Workouts

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What is the best way to preserve muscle on a water fast? How do you avoid muscle catabolism during fasts? We talk about fasted workouts and why strength and resistance training on a prolonged fast is your best friend.

Why we need to strength train during a water fast


The absolute number one thing that made my fast way easier and ultimately more successful was what I’m about to share with you in this video so I hope you stick around.

If you’re new to the channel welcome, I’m MD and I talk about fitness for longevity on this channel. For those of you who’ve been with me for a while, you know that I’m a big proponent of fasting for metabolic fitness. In addition to daily time-restricted feeding of 16/8 I also do three-day water fasts twice a year. 

Ok now that that’s out of the way, I want to share with you a eureka moment I had during my most recent water fast, which was February 2021. That was my third water fast to date.

And what I realized during that fast was the importance of strength training during that water fast. 

Now this video is not to suggest you fast. While it is a wonderful tool for metabolic health, I would recommend you do the research on fasting and talk with your PCP before embarking on a fasting journey.

Alright so strength training during a water fast is different than strength training when you’re not on a water fast.

So when I refer to strength training in this video in the context of water fasting please note that I am referring to strength training that is slower-paced, fewer reps, more in between time allowing for more rest, and more isometric holds. It is not the strength training that will jack your heart rate up and give you that cardio as well.

Also for context, in this recent water fast I had been using 20 pound dumbbells on the strength program I was doing and decided to keep with that weight during the entire water fast. I wanted to see how far I could safely push my boundaries and perceived limitations so that was definitely a mind exercise in and of itself.

Alright so why do we need to incorporate strength training during a water fast?

The reason strength training is important during a prolonged fast is because it is critical for maintaining muscle mass. Typically people think of a fasted workout as an opportunity to deplete their glycogen reserves that happens in the first 24 to 36 hours, especially if you do any kind of cardio activity during that period. But after that your body still needs energy in the form of glucose and it has two options: your fat or your muscle. If you are not doing any strength training during your fast your body will use both fat and muscle as a source of energy. By contrast if you do strength training during your fast your body will identify muscle as something that needs to be preserved and therefore will focus on deriving energy from fat instead, through a process called gluconeogenesis.

If you don’t strength train during a water fast will you experience muscle catabolism, meaning lose muscle mass?

Peter Attia and Jason phone agree on the core principle which is that fasting is not inherently a catabolic process. Our bodies preferentially burn fat over muscle. What Peter Attia is arguing is that by doing resistance training during a fast, you are activating chemical pathways that promote muscle synthesis. Essentially this provides extra insurance against losing muscle during the fast. The study he links to is fascinating in that the placebo group on a starvation diet with no supplements completing intense activity lost no muscle mass. Additionally the added activity of resistance training amplifies the other positive metabolic aspects of fasting, including autophagy and gluconeogenesis. Keep in mind also that Jason Fung's assumptions are based on historical populations who are by default active during their fasts. Comparing them to the modern person whose typical day is sedentary means there is a critical uncontrolled variable in terms of baseline activity. My primary takeaway is that adding resistance training adds extra protection against muscle loss while offering a host of other beneficial effects. And speaking anecdotally both my husband and I have much more energy throughout the day when we add workouts to our prolonged fasts than when we don't.

That being said, maybe you have questions about blood sugar.

Ok so let’s quickly chat about blood sugar while fasting.

In a metabolically healthy person the body is very good at maintaining safe blood sugar levels even while fasting. In particular, during a fast your body is able to convert fat into glucose through a process called gluconeogenesis this ensures your blood sugar stays high even without eating anything.

To be honest, after working out I feel better than I did before the workout. And as we know, it's also critical for maintaining muscle mass during the fast. 


Alright so I hope you took away something valuable from this video. I’ve shared what the research says as well as my personal experience.

I will be curious how I feel during my next water fast as I plan to do strength training during that as well.

What about you? Have you tried a water fast? If so would you consider strength training during? Is this something you are interested in? And lastly, would you like me to make more videos on the topic of fasting and metabolic fitness? Let me know in the comments.

I’ll see you in the next one! Ciao for now :)