Are There Any Health Benefits to Water Fasting?

"Water fasting" is a specific variant of intermittent fasting short-term practice that is exactly what it sounds like—fasting for anywhere from 12 hours to several days with water being the only source of "nutrition" during that timespan. Since water is calorie-free, water fasting is essentially just fasting without consuming any other calorie-free liquids, such as coffee, tea, or diet soda.

Read on to learn more about the purported health benefits of water-only fasting and why it's been a topic of scientific/clinical interest in recent years.

Medical Disclaimer: While intermittent fasting may promote weight loss, you should seek professional medical advice before making drastic changes to your dietary habits.

What Is Water Fasting?

Water fasting is when a person deliberately abstains from all food and consumes only water for a certain period of time, usually 24 to 72 hours. It is an ancient and widely practiced form of fasting that has been used for religious, spiritual, and health purposes for centuries.

It's important to distinguish "water-only fasting" from other fasting approaches since the former requires you to drink water only during the fasting period; no coffee, pre-workout supplements, or non-caloric beverages (e.g. diet soda).

During a water fast, it's best to avoid intense physical exertion. Going for a walk or other light physical activity should be fine, though.

That being said, time-restrictive eating is not for everyone; some people will experience adverse effects that make water-only fasting impractical. Highly restrictive eating regimens also carry health risks and may contribute to eating disorders [1]. The safest way to perform strict water fasting is in a supervised setting with the guidance of a qualified medical professional or healthcare provider [2].

What Are the Health Benefits of Water Fasting?

The heterogeneity of studies on fasting and time-restricted feeding makes it difficult to attribute health benefits to any specific scheme and compare them directly. Thus, the purported therapeutic effects of "water fasting" may very well apply to a more traditional intermittent fasting regimen that allows for the intake of other non-caloric liquids during the fasting window.

A growing body of literature suggests there are prophylactic benefits of (water) fasting for conditions like cardiovascular disease, metabolic syndrome, type-2 diabetes, and potentially even cancer [3]. Many of these studies note that short-term fasting significantly reduces blood pressure, improves insulin sensitivity, enhances immune function, and attenuates digestive system issues.

However, there's still controversy over whether or not the acute benefits of periodic water fasts translate to the long-term. For example, some short-duration studies show that water fasting lowers low-density lipoprotein (LDL) cholesterol levels, which may lead to a reduced risk of heart disease [4, 5]. (High LDL cholesterol and high blood pressure are primary risk factors for cardiovascular disease.) Further evidence supports that intensive short-term fasting (i.e. a 72-hour water fast) induces pronounced innate immune system remodeling [6].

Yet, lengthier studies of water fasting show no significant difference in cardiovascular disease risk factors when compared to a calorie-matched placebo diet (e.g. eating throughout the day) [7, 8]. Moreover, prolonged water fasts (multiple days) can lead to acute adverse effects, which is why it is advisable to complete them under medical supervision.

To reiterate, water fasting is just one of the several intermittent fasting protocols out there; it's unclear if water-only fasting produces greater benefits than other fasting regimens. Nevertheless, periodic water fasting may prove beneficial as an alternative or conjunctive therapy for numerous chronic diseases.

Can Water Fasting Help Me Lose Weight?

During a water fast, you restrict all calorie and nutrient intake for 12+ hours. Naturally, this can provoke weight loss by making it easier to undershoot your energy/calorie needs. While weight loss may occur after extensive water fasting, quickly losing body weight by essentially starving yourself for many hours, maybe even days, is not sustainable for most people [9]. Additionally, following a diet where you are only drinking water for the majority of the day may lead to nutrient deficiencies and malnutrition [10].

Rather than using water fasting in hopes of shedding pounds rapidly, it's more important to focus on overall portion control, food selection, and total energy intake. Continuous energy restriction, regardless of meal timing, is the key to sustainable weight loss. Start by reducing your consumption of processed foods and replace them with things like fruits and vegetables, complete protein sources (e.g. whey protein isolate), complex carbs, and quality fats.

Can Intermittent Fasting Be Part of a Healthy Diet?

Following a fasting protocol can be beneficial for certain health conditions, such as metabolic syndrome, type-2 diabetes, hypertension, hyperlipidemia, and potentially obesity [11]. However, there is a need for more compelling research to support the potential health benefits of extended water-only fasting.

Proceed with a sense of caution as water fasting to lose weight is not always wise; in some cases, it may work against you by making it harder to stick to the plan after you've reached your goal body weight, ultimately leading to "rebound" weight gain.