Your ultimate science based guide to fully reversing muscle loss during water fasting

Written by , Last updated: September 25, 2017

Welcome to my science based guide on water fasting and muscle loss.

I'll show you the science on how much muscle mass you can expect to lose during a water fast. I'll also show you exactly what you need to do, to fully prevent that unnecessary loss of muscle mass.

Muscle loss during water fasting (and how to reverse it)

If you want to learn more about how to actually go through with a water fast, you can check out my beginner's guide to water fasting.

But if you already know the basics, you can read my advanced guide to speeding up fat loss during a water fast.

Now that you know what my other water fasting guides are about, here's a quick overview of what's covered in this one:

Muscle loss during water fasting, a mixed diet, and a ketogenic diet

I found an awesome study that took a really close look at muscle loss during water fasting, a ketogenic diet, and a mixed diet.

The people on a mixed diet (with normal amounts of fats and carbs) ate 800 calories a day. The people on the ketogenic diet (with lots of fats and almost no carbs) also ate 800 calories per day.

And of course, the people doing a water fast, got in 0 calories a day.

Here are the amazing results the scientists came up with:

Weight loss Fat loss Muscle loss Water loss
Mixed diet 277.9 g/day 166.7 g/day 9.5 g/day 101.7 g/day
Ketogenic diet 446.6 g/day 163.4 g/day 17.9 g/day 265.3 g/day
Water fasting 750.7 g/day 243.1 g/day 50.4 g/day 457.2 g/day

At first glance, the table tells you that you'll lose muscle mass 5 times faster during a water fast than on your standard, 800-calorie weight loss diet (50 grams a day versus 10 grams a day).

But there's a catch.

The speed of muscle loss isn't the only thing that matters

While it's true that water fasting will destroy the most of your muscle mass per day, you also have to look at how quickly your total weight (or better yet, your body fat) will be coming off.

So let's say you wanted to lose 20 kilograms (44 pounds) of total weight (this is how most people set their weight loss goals anyway).

Here's how long that would take on a water fast, a mixed diet, and a ketogenic diet:

Days Fat loss Muscle loss Water loss
Mixed diet 72 days 12.0 kg 0.7 kg 7.3 kg
Ketogenic diet 45 days 7.3 kg 0.8 kg 11.9 kg
Water fasting 27 days 6.5 kg 1.3 kg 12.2 kg

As you can see from the second table, you won't actually lose 5 times more muscle mass on a water fast than on your standard diet. In fact, you won't even lose twice as much muscle mass.

Because, even though you'll be destroying more muscle per day on a water fast, you'll also reach your weight loss goal a lot faster (almost 3 times as fast), which is why you'll lose a lot less muscle mass in total.

There's also the issue of you losing a lot of water weight (instead of laser-targeting that stubborn body fat), but I won't go deeper into comparing these three diets here.

The point of my guide is to show you exactly how much muscle you can expect to lose during a water fast (and what you can do to 100% reverse that loss).

So let's an even closer look at the loss of muscle mass during a water fast.

A daily breakdown of muscle loss during a 21-day water fast

The table above, the one that says you'll be losing about 50 grams of muscle mass per day, may fool you into thinking that you'll be losing 50 grams of muscle every single day.

But the truth is, you'll be losing a lot more muscle mass in the early days of your fast than in the later stages of your fast.

Here's what one study on muscle loss during water fasting found out:

DayMuscle loss
169 grams
261 grams
362 grams
458 grams
553 grams
649 grams
737 grams
842 grams
935 grams
1033 grams
1127 grams
1226 grams
1325 grams
1424 grams
1523 grams
1622 grams
1717 grams
1816 grams
1918 grams
2016 grams
2115 grams

So there you go. Thanks to the study, we can see a complete daily breakdown of muscle loss during water fasting.

On to the one last thing we need to get out of the way...

How to fully reverse the loss of muscle during water fasting?

Let me just come out and say that there's no way of preventing the destruction of your muscle mass if you insist on doing a "pure" water fast.

But if you're willing to get in a tiny amount of protein (not necessarily as solid foods), then you can fully reverse any destruction of your muscle mass.

According to research, all you need is around 0.6 grams of protein per pound (or 1.3 grams of protein per kilogram) of your "ideal body weight".

And the best part?

If you're willing to eat that small amount of protein (or even drink them down in a form of protein isolate), you could fully reverse any loss of muscle mass WITHOUT slowing down fat burn.

Because, as long as you stay within proper limits, it's quite possible to get in enough protein without breaking your fast.

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Actionable summary

As you saw, water fasting can destroy about 5 times as much muscle mass per day, than your standard, 800 calories a day, mixed diet.

But the muscle loss during a water fast isn't as critical, because you'll also reach your weight loss as much as 3 times faster than on a standard diet (meaning you won't lose nearly as much muscle mass in total).

But no matter how you spin it, the loss of muscle mass is pretty much inevitable during water fasting (that's IF you insist on doing a pure water fast).

But if you can eat (or drink down) 0.6 grams of protein per pound (or 1.3 grams of protein per kilogram) of your "ideal body weight", you can fully reverse the loss of muscle mass.

(And you get to do it without slowing down those sky-high fat burn rates water fasting CAN deliver.)

David Brown

Hi, I'm David. This is what I'm best known for:

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