Benefits Of A 24 Hour Fast Once A Week

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Fasting can be a polarizing concept in the diet and nutrition world, especially when it comes to doing a prolonged fast, such as a 24 hour fast once a week.

Some dietitians and healthcare providers say that fasting is detrimental to your health and does not promote weight loss in a sustainable way.

On the other hand, some health experts and nutrition professionals believe fasting can be a healthy and effective means of losing weight, burning fat, reducing the risk of certain diseases, and even bettering overall health.

In this article, we will investigate the benefits of a 24 hour fast once a week.

We will cover: 

  • What Can You Have During a 24 Hour Fast?
  • 13 Benefits of a 24 Hour Fast Once a Week

Let’s jump in!

24h in red letters with a stop watch next to it.

What Can You Have During a 24 Hour Fast?

A 24-hour fast also called a 24-hour water fast, involves abstaining from all food and calorie-containing beverages for 24 hours.

You can have water, plain herbal tea with no added sweeteners, seltzer or club soda, or black coffee.

Adding electrolytes to your water is not just permissible but a good idea. A good option for a non-caloric electrolyte powder is Ultima.

Most people also say that black coffee is fine as well.

One cup (240 ml) of black coffee contains approximately 3 calories and just trace amounts of protein, fat, and minerals, so the nutrient content is so low that even a couple of cups of black coffee won’t really induce any metabolic changes or take you out of a fasted state.

However, adding caloric sweeteners, cream, MCT oil, milk, or grass-fed butter will break your fast.

Someone holding a cup of coffee.

13 Benefits of a 24 Hour Fast Once a Week

The benefits of a 24 hour fast once a week can include the following:

#1: A Weekly 24-Hour Fast Can Promote Weight Loss

One of the potential benefits of a 24 hour fast once a week is weight loss, and indeed the prospect of losing weight is one of the primary reasons that people try any sort of fasting, whether a standard time-restricted eating intermittent fasting diet (like 18/6 intermittent fasting) or a weekly 24-hour fast

Evidence suggests that fasting can promote weight loss and favorable improvements in body composition. 

For example, a review of 27 intermittent fasting dietary interventions found that all 27 studies resulted in weight loss of 0.8% to 13.0% of the starting weight with no serious adverse events. 

A person wrapping a measuring tape around their waist.

To lose weight, you have to generate a caloric deficit, which involves consuming fewer calories than you burn.

It takes a caloric deficit of 3,500 calories to lose one pound of body fat.

Therefore, if you follow any type of traditional, calorie-restrictive diet, this means that you need to consume 500 fewer calories per day than you burn every day to lose one pound per week.

Although this strategy works for some people, others find that doing a 24-hour fast once per week is more sustainable than modest deprivation every day.

Depending on your daily caloric needs, a 24-hour fast once a week may be almost all you need to do to generate the 3,500-calorie deficit for one pound of fat loss.

Even if you normally consume well under 3,500 calories per day, if you go a full 24 hours without taking in any calories, you’ll be well on your way to creating that energy deficit.

Then, you’ll only need to cut calories slightly the other six days of the week.

With that said, most studies demonstrating the weight loss benefits of fasting note that not everyone experiences weight loss from fasting.

The effectiveness of a 24-hour fast once a week for weight loss will depend on your overall caloric balance for the week; if you can sustain a caloric deficit from fasting without rebound compensatory eating the subsequent days, then you will lose weight.

A person holding out the waistband of their jeans, showing weight loss.

#2: A Weekly 24-Hour Fast May Reduce the Risk of Cardiovascular Disease

Although most people who take on a 24-hour fast once a week are motivated to do so by the potential fat loss benefits, there are other potential physical and mental health benefits of a 24-hour fast.

Research suggests that routine, periodic 24-hour water fasting can potentially reduce the risk of coronary artery disease (CAD), one of the leading causes of death for adults in the United States.

Researchers noted that a 24-hour water fast reduced levels of Trimethylamine N-oxide (TMAO), which is a compound produced by intestinal bacteria that has been associated with an increase in the risk of CAD.

Subjects had baseline TMAO levels that averaged 27.1 ng, but these levels dropped significantly after fasting 24 hours to 14.3 ng, representing a beneficial drop of 10.8 ng.

In contrast, after normal eating days, TMAO levels actually increased to 28.2 ng, a deleterious increase of +2.6 ng.

Although TMAO levels returned to baseline by 48 hours after the 24-hour water fast, the researchers note that having that 72-hour window where the levels were lower than baseline (during the fast plus the 48 hours afterward) helps reduce the overall weekly exposure of the body to harmful TMAO.

For this reason, it seems like a 24-hour fast every week can help reduce the risk of heart disease.

A glass of water is being poured.

#3: A Weekly 24-Hour Fast May Reduce the Risk of Metabolic Syndrome

Studies suggest that a 24-hour fast once a week may reduce the risk of metabolic syndrome because 24-hour fasts reduce LDL (“bad”) cholesterol and triglycerides, increase HDL (“good”) cholesterol, and reduce body fat.

#4: A Weekly 24-Hour Fast May Help Fight Certain Cancers

Although human studies are lacking, evidence from animal studies suggests that fasting may help the body fight certain cancers by making tumor cells more sensitive to chemotherapy agents.

This makes it easier to kill off the tumors, especially in cases of aggressive tumor growth.

#5: A Weekly 24-Hour Fast May Help Reduce the Risk of Heart Attack and Stroke

Evidence suggests that intermittent fasting has a similar positive effect on cardiovascular and brain health as aerobic exercise by increasing brain-derived neurotrophic factors.

This is thought to reduce oxidative damage and increase cellular stress resistance, which, in turn, increases the resistance of heart and brain cells to ischemic injury, reducing the risk of heart attack and stroke. 

A piece of paper with the words growth hormone on it and lap equipment surrounding it.

#6: A Weekly 24-Hour Fast May Increase Growth Hormone

Human growth hormone (HGH) increases muscle building and cellular repair and accelerates fat burning.

Levels of HGH are increased after heavy resistance training, which is one of the main reasons why positive anabolic effects and cellar repair occur after this type of exercise.

There’s also evidence to suggest that one of the benefits of a 24 hour fast once a week, or intermittent fasting, can increase the production of HGH, eliciting similar benefits. 

#7: A Weekly 24-Hour Fast May Stimulate Autophagy

Extended fasting, such as going 24 without eating, induces autophagy, which is a cellular clean-up process whereby the healthy cells get rid of cellular waste products and dead and dying cells.

The process of autophagy improves cellular health, reduces inflammation, supports new cellular growth, and is said to stave off aging. 

#8: A Weekly 24-Hour Fast Can Reduce Oxidative Stress

One of the main benefits of a 24 hour fast once a week is that it may help defend your body from oxidative stress, which is damage that occurs from free radicals and reactive species.

Oxidative stress is associated with the premature breakdown of proteins and cellular membranes, alterations to DNA, and cellular aging.

Therefore, by helping the body fend off oxidative stress, 24-hour water fasts can help protect against cellular damage and can potentially combat aging.

A chalkboard with the word inflammation on it and a stethescope.

#9: A Weekly 24-Hour Fast Can Reduce Inflammation

Periodic fasting can reduce inflammation, which is a key driver underlying many chronic diseases such as obesity, metabolic syndrome, type 2 diabetes, heart disease, and certain cancers.

#10: A Weekly 24-Hour Fast May Help Improve Brain Health

The benefits of fasting for 24 hours are not solely confined to the body; there are benefits of a 24 hour fast once a week for the brain as well.

For example, animal studies suggest that periodic fasting may stimulate neurogenesis (the growth of new neurons) and may increase longevity.

#11: A Weekly 24-Hour Fast May Improve Insulin Sensitivity 

Evidence suggests that intermittent fasting reduces insulin levels, reducing the risk of insulin resistance while also supporting fat loss.

A cup of coffee and a piece of paper that says boost your metabolism. One of the benefits of a 24 hour fast.

#12: A Weekly 24-Hour Fast May Increase Your Metabolic Rate

Studies suggest that although prolonged fasting can decrease your metabolic rate, short-term caloric restriction with periodic fasts can increase your metabolic rate

Researchers think that fasting induces a hormonal milieu that increases lipolysis, or the breakdown of body fat for energy.

This is largely due to the fact that fasting decreases your insulin levels and increases human growth hormone and norepinephrine. 

A faster metabolic rate can support fat loss because the more calories you burn at rest, the easier it will be to consume fewer calories than you’re eating.

#13: A Weekly 24-Hour Fast Can Reduce the Risk of Certain Diseases

Due to benefits such as reducing insulin and increasing autophagy, a 24-hour fast once a week may help reduce the risk of various diseases, such as diabetes, certain cancers, and neurodegenerative diseases, such as Alzheimer’s disease.

Although doing a 24-hour fast once a week isn’t necessarily safe or tenable for everyone, it can be a wonderful way to boost health and support weight loss goals for others.

If you are interested in fasting for 24 hours to reap the 24 hour fast benefits, speak with your doctor for personalized recommendations.

If you would like to look into other intermittent fasting diets, check out our guide.

A notebook with the words intermittent fasting on it, a clock, and an empty plate with silverware.
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Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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