Welcome to my science-based guide through the amazing benefits of water fasting.

For most people, the single most important benefit of water fasting is weight loss.

But what many people don't know is that modern science has discovered water fasting can literally "kill" your hunger and cravings (you'll see the science on this in a bit).

And the third benefit of water fasting is its potential to help with cancer treatment (and dealing with the side effects of chemotherapy), but science has only started to take a closer look at that.

Another major beneficial effect of water fasting is that it boosts autophagy, a natural "cleanup" process in our bodies (but more on this in a bit).

Before we get started, here's a quick overview of everything that's covered in this part of the guide:

Weight loss

Yes, weight loss is easily the number one benefit of water fasting.

Because you're drinking only water (and getting in no calories at all), that number on your bathroom scale will drop extremely fast.

And while water fasting will allow you to burn fat at an extremely accelerated pace, you'll also be losing a lot of your lean body mass.

Your lean body mass is basically everything in your body besides body fat, but during a water fast, you will primarily lose water weight, glycogen- and sodium-bound water weight, and muscle mass.

To find out more about what types of weight you will actually end up losing during a water fast, go to the part of the guide that deals with the specifics of water fasting and weight loss.

In that part you will find all the details on how much weight you can expect to lose, how much that lost weight will be muscle mass (and most importantly, how to prevent this unnecessary loss of muscles).

On to the next amazing benefit of water fasting, almost a complete disappearance of hunger and appetite.

Loss of hunger and appetite

A lot of people look into water fasting to quickly lose some weight.

But most of them decide not to do it, simply because they believe there is no way they you could go completely without food.

If you're one of those people, then I have some surprising science for you:

In a study[1], where a group of people fasted for two weeks, they proved that hunger and cravings almost completely disappear during a water fast.

In another water fasting study[2], people fasted for as much as 117 days!

(Those people fasted under strict medical supervision, do don't even think about fasting for that long on your own.)

And even though some of the people in the study went without food for more than 3 months, scientists also confirmed that "hunger was virtually absent" throughout the study.

From my personal experience with water fasting, I can tell you that as long as you can get through that first awkward phase (the first two days or so), cravings and hunger DO become way easier to handle.

During one of my fasts, I literally felt like I no longer care about food.

And while water fasting definitely isn't a walk in the park, it can actually be easier to handle than some of the less restrictive diets.

So while in theory, eating 500 calories a day might seem easier to handle than no food at all, tiny amounts of food may actually trigger more hunger and cravings than if you eat no food at all.

Naturally, having your hunger and appetite practically disappear is a very unique benefit of water fasting.

On to the next amazing benefit of water fasting.

Cancer and chemotherapy

Ok, before we can even being to discuss science on water fasting and potentially life-threatening diseases like cancer, a HUGE WARNING:

DO NOT act on any information you read here (or on any other website for that matter) on your own.

You can print out the studies mentioned here, read them like your life depended on it, but ALWAYS discuss your options with a qualified medical professional (your doctor).

With that out of the way, here's some science that proves water fasting could actually be effective for treating cancer:

In one study[3], they discovered that water fasting can be as effective as chemotherapy drugs in delaying tumor growth in certain types of cancers.

On top of that, it can increase the effectiveness of chemotherapy drugs (again, only in certain types of cancers).

Another piece of research[4] looked at cancer patients who fasted for different amounts of time before and after chemotherapy.

And water fasting was able to reduce, or in some cases completely eliminate the negative side effects of chemotherapy.

Things like fatigue, weakness, hair loss, headaches, nausea, vomiting, diarrhea, numbness, tingling...

A whole lot of research needs to be done before the final verdict on treating cancer with water fasting can be reached

But the current scientific evidence certainly suggests that water fasting could potentially replace, or at least boost the effectiveness of certain chemotherapy drugs certain types of cancer treatments.

On to another amazing benefit of water fasting.


Autophagy is a natural and evolutionary process of cellular regeneration and cell material recycling.

In other words, certain cell materials are taken to the "cellular garbage cans" to be deconstructed and turned into new building blocks and energy used for cellular renovation and regeneration.

And while the natural and health-friendly process of autophagy is constantly unfolding in our bodies, it stays pretty damn slow, for as long as you stick with the regular three-five meals a day.

But during a water fast, autophagy in your body will be greatly accelerated, simply because you're not delivering any new calories to your cells[5].

This means that during a water fast, your cells will happily start the natural process of cellular "cleanup", renovation and regeneration.

Which makes autophagy yet another awesome benefit of water fasting.

Summary (actionable takeaways)

In this part of my science-based guide that covers the specific benefits of water fasting, your learned that water fasting:

  • can be extremely efficient for weight loss, but on top of losing a lot of body fat, you will also lose some of your lean body mass (which can luckily be prevented),
  • causes almost a complete disappearance of hunger and appetite, but you'll have to stick with it for a day or so before this welcome benefit kicks in,
  • can be helpful when it comes to treating cancer and dealing with the negative effects of chemotherapy (but ALWAYS consult your doctor on this)
  • triggers the natural "cleanup" process in your body called autophagy, that greatly speeds up the renovation and regeneration on a cellular level.

Written by

Rok Sprogar is a NASM Certified Nutrition Coach (NASM-CNC) and a NASM Certified Weight Loss Specialist (NASM-WLS) who has been contributing highly actionable and science-based content to Leanhigh.