Often, we’re told happiness and self-improvement can come only through addition—it’s the consumer culture we live in.

There is nothing inherently wrong about this. Eating healthy food, supplementing, and taking some time to better yourself through exercise or meditation are all additive actions that (hopefully) add something to our lives and help us achieve our best.

But, there may also be another side to human enhancement, one that involves restriction, rather than addition.

By restriction, we are referring to the practice of fasting, the (recently mainstream) practice of abstaining from food for a period of time. Everyone from Silicon Valley CEOs to medical professionals are recommending fasting as the next best thing in human optimization, the key to peak mental and physical performance.

This ancient health practice is getting a shot in the arm with science and data. Here’s how you can try water fasting, and what to expect when you do.

Water Fasting 101

Most proponents of fasting claim that humans evolved to go without food for prolonged periods of time. Fasting is natural, in this way.

In fact, it was probably a necessity. Food wasn’t always available. It was hard to obtain. No supermarkets in the paleolithic era. For this reason, our bodies seem to have several mechanisms that allow us to survive prolonged periods of time without taking in external energy sources (food). The ability to oxidize fat for fuel as well as the ability to produce and use ketones are two such pathways. Without them, we’d often be hangry, or worse, dead.

Substantial benefits occur when we are able to activate these conserved evolutionary pathways through fasting, making the body more robust.

Many systems become stronger, more resilient. But how do we tap into these systems in modern day, with a burger joint on every corner?

One way is through water fasting. As the name suggests, water fasting is the practice of going without food or any calorie-containing beverages for a period of around 24 – 72 hours. The only thing permitted? Good old H20. Some claim that coffee, sparkling water, and other non-caloric beverages are allowed. We’ll leave the rules up to you on this one.

People partake in water-only fasts for various reasons—medical and healing purposes, for spirituality and religious reasons, weight loss, mental clarity, longevity, and “gut resetting.” While it’s been commonly used for obesity treatment since around 1915, fasting has health benefits above and beyond just weight loss.

Water Fasting vs. Intermittent Fasting and Time Restricted Eating

“Fasting” is a broad term that really just means “not eating” and therefore can mean a variety of things to different people. You’ll hear fasting mentioned online and in the media, with little specificity on what protocol is actually being employed. Several iterations of fasting are popular, so let’s differentiate them a bit.

Intermittent fasting (IF) refers to a “reduced meal frequency.” Again, while time lengths can vary, it often takes the form of a periodic (hence, intermittent) period of fasting that last around 24 – 48 hours. Some people do one weekly, some monthly. Intermittent fasting can also take the form of alternate-day fasting, where you eat every other day, or a “fasting mimicking” protocol where calories are drastically reduced for a few days at a time.

Time-restricted feeding (TRF) or time-restricted eating (TRE) involves eating within a certain window and then fasting for the rest of the day and night. Popular protocols for IF/TRF include 16:8, 18:6, and 20:4—where the first number refers to the fasting period and the latter, the feeding period.

Water fasting, on the other hand, typically involves a bit longer of a fasting period. 24, 48, and 72-hour water-only fasts are most common, but some might even push a fast out to 5 or 7 days. Some people may do these 1 – 7 day water fasts once a month or a few times per year. Water only fasting can be seen as a more extreme version of IF/TRE that might have unique and distinct benefits from the daily practice of a shorter fasting window.

Benefits of Water-Only Fasting

Three square meals a day—this is commonly accepted as the “normal” paradigm of daily food consumption. If this suits your lifestyle and you enjoy it, then there is nothing wrong with this way of eating. It’s your health, and your life.

However, there is something to be said about occasionally restricting ourselves using things like water fasting and IF/TRE. Giving a little “shock” to the body with an extended fast can be a good thing, especially when we’ve trained it to constantly expect incoming energy. Think of fasting as training for cells—it’s a process by which we can make them stronger by first stressing them out a bit. This and other health benefits of fasting have been a topic of study for decades.

Autophagy: Cellular Garbage Man

You may have heard this buzzword in most nutrition and health spheres: autophagy. Often compared to some sort of recycling or garbage disposal system, autophagy (meaning “self-eating”) is a conserved process that involves the degradation of organelles, proteins, and other large molecules from the body, recycling some of their components while getting rid of others.

Why do we need autophagy? Throughout daily life, some molecules become damaged or senescent (they stop dividing and become useless). We need to get rid of these lingering damaged molecules somehow, and this is where autophagy comes into play. Cellular “trash” is taken up by compartments called autophagosomes, delivered to breakdown machines known as lysosomes, and then basically ripped apart. From the waste products, new building material is created, and used to aid in cellular repair, regeneration, and immune system regulation.

Fasting is one way to activate autophagy and clear out our body’s damaged machinery.

While our ability to measure autophagy in humans is elementary at the moment, there have been a few studies in rodent models that document the induction of autophagy in response to fasting. For instance, after 24 – 48 hours of fasting (only water allowed), autophagy was enhanced in neurons in the brains of mice. This was confirmed by the increase in the number of garbage-clearing autophagosomes throughout the brain. Similar periods of water-only fasting in mice (24 – 48 hours) are sufficient to upregulate autophagy in the liver, kidney, muscle, pancreas, thymus, and even the lens of the eye.

24 – 48 hours in mice represent a much longer time period in humans—so take these results with caution. The same robust autophagy benefits in humans might only arise via longer fasting periods.

Nevertheless, autophagy may still be activated in response to similar fasting time periods in us humans—just at lower levels and after a bit longer period of time.

Reducing Oxidative Stress

Oxidative stress, sometimes also mentioned along with inflammation, is a process by which highly-reactive molecules in our body cause damage to cells and DNA. This is often a result of an imbalance between pro-oxidants and antioxidants and a highly activated immune system.

Oxidative stress is known to play a role in the development and worsening of many medical conditions like heart disease, chronic kidney disease, neurodegenerative disease, and cancer. It’s even claimed to be one of the causes of aging.

Can fasting lower oxidative stress? The research indicates a strong possibility.

Since one of the known sources of reactive oxygen species and inflammation is the metabolism of food, it seems likely that short term food restriction will lower production of these molecules that are released during metabolism.

An 11-day water fast was shown to significantly reduce oxidative stress markers in adults; this was accompanied by several other benefits including enhanced kidney function. Another study demonstrated that, while oxidative stress was not reduced, 48 – 60 hours of fasting made cells more resistant to oxidative stress induced by chemotherapy. There are several published case reports that autoimmune diseases, characterized by risk factors like chronic inflammation, can be completely resolved with 7 – 24 days of water-only fasting.

The benefits of water fasting may partly be owed to ketones. It has been shown that the ketone body Beta-hydroxybutyrate (BHB), whether given exogenously or increased through fasting/calorie restriction or a ketogenic diet offers significant protection against oxidative stress. It does this by increasing the expression of genes related to protective stress responses and antioxidant pathways. This may be why supplementing with exogenous ketones has been shown to reduce inflammatory processes in human and animal cells, and why ketogenic diets show such promise for improving medical conditions characterized by dysregulated metabolism.

Weight Loss and Body Composition

Short-term water fasting has many benefits, but weight loss might not be one of the most robust.

In 24 – 48 hours, most of the weight you lose will be the result of shedding a significant amount of water weight and/or a minor loss in muscle glycogen, along with smaller amounts of muscle and fat.

For long term fat loss, a more prolonged (medically supervised) water-only fast may be needed, or a dedicated regimen of intermittent fasting undertaken for a significant length of time.

Yet, some studies do demonstrate significant weight loss after short term water fasts.

After a 24-hour water-only fast, healthy adults experienced a decrease in weight which was maintained for up to 48 hour post-fast. Larger changes in body mass are seen with longer fasts. In an older study consisting of 46 obese participants who were put on a 14-day fast, average weight loss was 7.6 kilograms. A similar time period in rats led to significant weight loss, body fat loss, and an increase in relative lean mass (meaning more fat was lost).

My 7-Day Water Fast Experience

It’s funny the things you find while browsing the Internet at 4am. A couple weeks ago while glued to my laptop at precisely this time, I came across a Youtube video called “7 DAY WATER FAST — NO FOOD OR DRINK FOR A WEEK.” It had a whopping 7.4 million views.

Though sleepiness was beginning to set in and the video was a bit longer than I would have liked, I decided to watch; I was intrigued. How could a person only drink water for a week? What sort of insane willpower would drive this kind of self-torture?

The video depicted the experience of a man called Lou who decided to only drink water for a full week, in hopes it would help cure his chronic aches and pains stemming from rheumatoid arthritis. Great, I thought, another pop science nutrition fad with no real empirical backing. Surely it’s one of those things that people label as a miracle cure, only to find out years later it actually causes permanent damage to your body. Like diet pills or fruit-only meal plans.

But as I kept watching video, the idea of water fasting started to grow on me. After Lou’s 7 day fast, the guy went from experiencing debilitating daily back pain to having absolutely no pain at all. Interest piqued, I decided to do more in-depth research on the concept of water-fasting. And things began to make sense. I found multiple scientific studies from established sources backing up the idea of fasting, as well as articles written by doctors and nutritionists praising it for its benefits.

At that’s when I decided, at 5am, that I was going to do a water fast.

What is Water-Fasting?

Fasting has become increasingly popular in the US today. According to MedicalNewsToday and the New York Times, fasting dates back thousands of years, having been historically practiced all around the word for spiritual and religious reasons. However, it is only more recently that fasting has emerged in pop-culture as a part of the wellness and mindfulness movement. People often pair fasting with mindfulness practices like meditation.

You may be familiar with intermittent fasting, a feeding method endorsed by celebrities like Hugh Jackman,