13 Benefits Of A 24-Hour Fast Once A Week

How fasting can potentially improve your overall health.

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

Some dietitians and healthcare providers say fasting is detrimental to your health and does not sustainably promote weight loss.

On the other hand, some health experts and nutrition professionals believe fasting can be a healthy and effective means of losing body 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.

Let’s jump in!

An empty plate and alarm clock.

What Is 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 drink water, plain herbal tea with no added sweeteners, seltzer, 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.

One cup (240 ml) of black coffee contains approximately three 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.1van Dam, R. M., Pasman, W. J., & Verhoef, P. (2004). Effects of Coffee Consumption on Fasting Blood Glucose and Insulin Concentrations: Randomized controlled trials in healthy volunteers. Diabetes Care27(12), 2990–2992. https://doi.org/10.2337/diacare.27.12.2990

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

Someone holding a cup of coffee.

What are the Potential Health Benefits of Doing a 24-Hour Fast Once a Week?

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

#1: Can Promote Weight Loss

One of the potential benefits of a 24-hour fast once a week is weight loss.

The prospect of losing weight is one of the primary reasons people try any type of fasting regimen, whether a standard time-restricted eating intermittent fasting diet (like 18/6 intermittent fasting), alternate-day fasting, or a weekly 24-hour fast.

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

So, how much weight do you lose in a 24-hour fast?

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.2Welton, S., Minty, R., O’Driscoll, T., Willms, H., Poirier, D., Madden, S., & Kelly, L. (2020). Intermittent fasting and weight loss. Canadian Family Physician66(2), 117–125. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7021351/

A person wrapping a measuring tape around their waist.

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

Losing one pound of body fat takes a caloric deficit of 3,500 calories.

Therefore, if you follow any 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 calorie intake and 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; if you can sustain a caloric deficit from fasting without rebound compensatory eating the subsequent days, you will lose weight.

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

#2: 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, such as improved heart health.

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 two days (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: May Reduce the Risk of Metabolic Syndrome

Studies suggest that a one day 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.3Horne, B. D., Muhlestein, J. B., Lappé, D. L., May, H. T., Carlquist, J. F., Galenko, O., Brunisholz, K. D., & Anderson, J. L. (2013). Randomized cross-over trial of short-term water-only fasting: Metabolic and cardiovascular consequences. Nutrition, Metabolism and Cardiovascular Diseases23(11), 1050–1057. https://doi.org/10.1016/j.numecd.2012.09.007

‌#4: 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.4Di Biase, S., Lee, C., Brandhorst, S., Manes, B., Buono, R., Cheng, C.-W., Cacciottolo, M., Martin-Montalvo, A., de Cabo, R., Wei, M., Morgan, T. E., & Longo, V. D. (2016). Fasting-Mimicking Diet Reduces HO-1 to Promote T Cell-Mediated Tumor Cytotoxicity. Cancer Cell30(1), 136–146. https://doi.org/10.1016/j.ccell.2016.06.005

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

#5: May Help Reduce the Risk of Heart Attack and Stroke

Evidence suggests intermittent fasting has a similar positive effect on cardiovascular and brain health as aerobic exercise by increasing brain-derived neurotrophic factors.5MATTSON, M., & WAN, R. (2005). Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. The Journal of Nutritional Biochemistry16(3), 129–137. https://doi.org/10.1016/j.jnutbio.2004.12.007

‌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: May Increase Growth Hormone

Human growth hormone (HGH) increases muscle building and cellular repair and accelerates fat burning.6Chikani, V., & Ho, K. K. Y. (2013). Action of GH on skeletal muscle function: molecular and metabolic mechanisms. Journal of Molecular Endocrinology52(1), R107–R123. https://doi.org/10.1530/jme-13-0208

‌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.7Home Page: The American Journal of Clinical Nutrition. (n.d.). Ajcn.nutrition.org. https://ajcn.nutrition.org/

‌#7: May Stimulate Autophagy

Fasting for an extended period, such as going 24 hours without eating, induces autophagy, which is a cellular clean-up process whereby healthy cells get rid of cellular waste products and dead and dying cells.8Bagherniya, M., Butler, A. E., Barreto, G. E., & Sahebkar, A. (2018). The effect of fasting or calorie restriction on autophagy induction: A review of the literature. Ageing Research Reviews47, 183–197. https://doi.org/10.1016/j.arr.2018.08.004

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

#8: 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.9Cienfuegos, S., Gabel, K., Kalam, F., Ezpeleta, M., Wiseman, E., Pavlou, V., Lin, S., Oliveira, M. L., & Varady, K. A. (2020). Effects of 4- and 6-h Time-Restricted Feeding on Weight and Cardiometabolic Health: A Randomized Controlled Trial in Adults with Obesity. Cell Metabolism32(3), 366-378.e3. https://doi.org/10.1016/j.cmet.2020.06.018

‌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 potentially combat aging.

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

#9: Can Reduce Inflammation

A fasting period of 24 hours 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: 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)10Baik, S.-H., Rajeev, V., Fann, D. Y.-W., Jo, D.-G., & Arumugam, T. V. (2020). Intermittent fasting increases adult hippocampal neurogenesis. Brain and Behavior10(1), e01444. https://doi.org/10.1002/brb3.1444 and may increase longevity.11Goodrick, C. L., Ingram, D. K., Reynolds, M. A., Freeman, J. R., & Cider, N. L. (1982). Effects of intermittent feeding upon growth and life span in rats. Gerontology28(4), 233–241. https://doi.org/10.1159/000212538

#11: May Improve Insulin Sensitivity 

Evidence suggests that intermittent fasting reduces insulin levels, reducing insulin resistance risk while supporting fat loss.12Hoddy, K. K., Gibbons, C., Kroeger, C. M., Trepanowski, J. F., Barnosky, A., Bhutani, S., Gabel, K., Finlayson, G., & Varady, K. A. (2016). Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting. Clinical Nutrition35(6), 1380–1385. https://doi.org/10.1016/j.clnu.2016.03.011

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

#12: May Increase Your Metabolic Health

Studies suggest that although prolonged fasting can decrease your metabolic rate, short-term caloric restriction with periodic fasts can increase your metabolic rate.13Teruya, T., Chaleckis, R., Takada, J., Yanagida, M., & Kondoh, H. (2019). Diverse metabolic reactions activated during 58-hr fasting are revealed by non-targeted metabolomic analysis of human blood. Scientific Reports9(1). https://doi.org/10.1038/s41598-018-36674-9

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

This is largely because fasting decreases 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: Can Reduce the Risk of Certain Diseases

Fasting is believed to combat various medical conditions and support overall well-being.

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.

What Happens to Your Body on a 24-Hour Fast?

The body needs energy to carry out its endless list of functions and, on a day-to-day basis, pulls its energy from glucose (a source of sugar), which we get from eating carbohydrates.

When these stores run out (around 18-20 hours after no eating), our body needs a Plan B. Because no glucose comes in, the body must create its own, mostly from stored fat.

Plan C will kick in after this period, where the body begins to break down muscle tissue as well, but with a 24-hour fast, we shouldn’t get to that point as we will replenish our glycogen stores shortly after 24 hours.

How Often Should You Do a 24-Fast?

A 1 day fast, or fasting for a full day, is generally a safe approach to weight loss and health once a week.

People with more experience fasting and are practicing alternate-day fasting may be able to do a 24-hour fast several times per week.

However, if this is your preferred weight loss diet approach, you should speak with your doctor beforehand to ensure that multiple 24-hour fasts per week will be safe and ideal for you.

Although doing a 24-hour fast once a week isn’t necessarily safe or tenable for everyone due to certain side effects, 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 wellness benefits of a 24-hour fast, speak with your doctor for personalized recommendations.

If you want to look into other intermittent fasting diets, check out our guide

References

  • 1
    van Dam, R. M., Pasman, W. J., & Verhoef, P. (2004). Effects of Coffee Consumption on Fasting Blood Glucose and Insulin Concentrations: Randomized controlled trials in healthy volunteers. Diabetes Care27(12), 2990–2992. https://doi.org/10.2337/diacare.27.12.2990
  • 2
    Welton, S., Minty, R., O’Driscoll, T., Willms, H., Poirier, D., Madden, S., & Kelly, L. (2020). Intermittent fasting and weight loss. Canadian Family Physician66(2), 117–125. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7021351/
  • 3
    Horne, B. D., Muhlestein, J. B., Lappé, D. L., May, H. T., Carlquist, J. F., Galenko, O., Brunisholz, K. D., & Anderson, J. L. (2013). Randomized cross-over trial of short-term water-only fasting: Metabolic and cardiovascular consequences. Nutrition, Metabolism and Cardiovascular Diseases23(11), 1050–1057. https://doi.org/10.1016/j.numecd.2012.09.007
  • 4
    Di Biase, S., Lee, C., Brandhorst, S., Manes, B., Buono, R., Cheng, C.-W., Cacciottolo, M., Martin-Montalvo, A., de Cabo, R., Wei, M., Morgan, T. E., & Longo, V. D. (2016). Fasting-Mimicking Diet Reduces HO-1 to Promote T Cell-Mediated Tumor Cytotoxicity. Cancer Cell30(1), 136–146. https://doi.org/10.1016/j.ccell.2016.06.005
  • 5
    MATTSON, M., & WAN, R. (2005). Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. The Journal of Nutritional Biochemistry16(3), 129–137. https://doi.org/10.1016/j.jnutbio.2004.12.007
  • 6
    Chikani, V., & Ho, K. K. Y. (2013). Action of GH on skeletal muscle function: molecular and metabolic mechanisms. Journal of Molecular Endocrinology52(1), R107–R123. https://doi.org/10.1530/jme-13-0208
  • 7
    Home Page: The American Journal of Clinical Nutrition. (n.d.). Ajcn.nutrition.org. https://ajcn.nutrition.org/
  • 8
    Bagherniya, M., Butler, A. E., Barreto, G. E., & Sahebkar, A. (2018). The effect of fasting or calorie restriction on autophagy induction: A review of the literature. Ageing Research Reviews47, 183–197. https://doi.org/10.1016/j.arr.2018.08.004
  • 9
    Cienfuegos, S., Gabel, K., Kalam, F., Ezpeleta, M., Wiseman, E., Pavlou, V., Lin, S., Oliveira, M. L., & Varady, K. A. (2020). Effects of 4- and 6-h Time-Restricted Feeding on Weight and Cardiometabolic Health: A Randomized Controlled Trial in Adults with Obesity. Cell Metabolism32(3), 366-378.e3. https://doi.org/10.1016/j.cmet.2020.06.018
  • 10
    Baik, S.-H., Rajeev, V., Fann, D. Y.-W., Jo, D.-G., & Arumugam, T. V. (2020). Intermittent fasting increases adult hippocampal neurogenesis. Brain and Behavior10(1), e01444. https://doi.org/10.1002/brb3.1444
  • 11
    Goodrick, C. L., Ingram, D. K., Reynolds, M. A., Freeman, J. R., & Cider, N. L. (1982). Effects of intermittent feeding upon growth and life span in rats. Gerontology28(4), 233–241. https://doi.org/10.1159/000212538
  • 12
    Hoddy, K. K., Gibbons, C., Kroeger, C. M., Trepanowski, J. F., Barnosky, A., Bhutani, S., Gabel, K., Finlayson, G., & Varady, K. A. (2016). Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting. Clinical Nutrition35(6), 1380–1385. https://doi.org/10.1016/j.clnu.2016.03.011
  • 13
    Teruya, T., Chaleckis, R., Takada, J., Yanagida, M., & Kondoh, H. (2019). Diverse metabolic reactions activated during 58-hr fasting are revealed by non-targeted metabolomic analysis of human blood. Scientific Reports9(1). https://doi.org/10.1038/s41598-018-36674-9
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and 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.

3 thoughts on “13 Benefits Of A 24-Hour Fast Once A Week”

  1. Great article! I tried a 24hr fast for the first time yesterday. Today i feel like I am high on drugs lol. I feel unbelievably good for a Monday. I’m sure this is due to the fast I did yesterday.
    I will plan to do this every Sunday if this is how it makes me feel.

    Reply

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.