24-Hour Fast: What are the benefits and risks?

February 28, 2023
| No Comments

"24 hours with NO FOOD?" 

"WHY DO THAT?"

 "I THINK I WOULD DIE..."

 

That is the usual responce I get when I mention this to friends or clients. Well… let me explain.

 

I have recently been experimenting with regular 24 hour fasting for health and weight loss benefits… My sunday fast (24 hours) is something I now look forward to and I though I would share the reasoning and justifications behind my decision to do this every week. 

 

 

Sit back, grab a coffee and enjoy this 5 minute read

What Is A 24-Hour Fast?

A 24-hour fast is a period where a person abstains from consuming any food or calories for 24 hours. It typically starts after dinner and lasts until the following day’s dinner.

 

During this time, it is still important to drink plenty of water and other non-caloric beverages to stay hydrated. Black coffee and green/black tea are generally accepeted as part of the protocol, but some protocols only allow for water.

The purpose of a 24-hour fast is to give the digestive system a break, promote weight loss, improve metabolic health, and potentially provide other health benefits.

Quick List Of Benefits Of 24-Hour Fasting

There are several benefits to doing a 24-hour fast, including:

 

      1. Digestive System Health: A 24-hour fast is giving the digestive system a break. During a fast, the body does not have to spend energy digesting food and can instead focus on repairing and rejuvenating.
      2. Weight loss: Fasting can help reduce calorie intake and boost metabolism, leading to weight loss.
      3. Improved insulin sensitivity: Fasting can help lower insulin levels, which improves insulin sensitivity, leading to better blood sugar control.
      4. Improved heart health: Fasting can reduce inflammation, lower blood pressure, and improve cholesterol levels, all of which are beneficial for heart health.
      5. Improved brain function: Fasting can increase brain-derived neurotrophic factor (BDNF), which is a protein that helps improve brain function and protect against neurodegenerative diseases.
      6. Increased longevity: Studies have shown that fasting can extend lifespan and promote healthy aging.
      7. Improved immune function: Fasting can help stimulate the immune system and reduce inflammation, which can help improve immune function.
      8. Reduced risk of chronic disease: Fasting has been associated with a reduced risk of chronic diseases, such as cancer, diabetes, and heart disease.

When does Fasting transition to 'Starvation Mode'?

The term “starvation mode” refers to a metabolic response that occurs when the body is deprived of food for an extended period. 

 

The body’s metabolism slows down to conserve energy and preserve body fat, which can make it more difficult to lose weight. However, the exact timing of when fasting becomes “starvation mode” is a matter of debate among experts.

 

Some studies suggest that the body may begin to enter starvation mode after as little as 16-24 hours of fasting, while others suggest that it may take several days of fasting before this response occurs.

For example, a study published in the American Journal of Clinical Nutrition found that after 72 hours of fasting, the metabolic rate decreased by an average of 8%, which is consistent with the body entering starvation mode (1).

 

Another study published in the Journal of Translational Medicine found that participants who fasted for 48 hours experienced a decrease in resting metabolic rate, but that this response was not significant enough to be considered starvation mode (2).

 

Overall, the timing of when fasting becomes “starvation mode” may depend on factors such as the individual’s body composition, level of physical activity, and the length and frequency of the fast.

1. Benefits Of 24-Hour Fast: Resting the Digestive System

One of the main benefits of a 24-hour fast is giving the digestive system a break. During a fast, the body does not have to spend energy digesting food and can instead focus on repairing and rejuvenating other systems. 


This can lead to improvements in gut health, as well as a reduction in inflammation and oxidative stress. In addition, fasting has been shown to improve insulin sensitivity and lower the risk of chronic diseases such as diabetes, cardiovascular disease, and cancer (3).

Research has found that even short periods of fasting can have a positive impact on gut health. 

 

A study published in the journal Cell Reports found that intermittent fasting, which includes periods of 24-hour fasts, can help to increase the diversity of gut microbiota, which is important for overall digestive health (4). 

 

Another study published in the journal Nutrients found that fasting can help to reduce inflammation in the gut and improve symptoms of inflammatory bowel disease (5).

Overall, giving the digestive system a break, through a 24-hour fast can have numerous benefits for overall health and well-being. Especially for those who regularly experience digestive system issues.

2. Benefits of a 24-Hour Fast: Weight loss:

Fasting reduces calorie intake, which can lead to weight loss. In one study, people who fasted for 24 hours lost an average of 1.2 kg (2.6 lbs) of body weight (6). This weight will later return when you re-feed (depending on how much you eat), however, your daily and weekly calorie intake will be reduced by the extended time period without food, resulting in some weight loss. 

Fasting can also increase metabolism, which may further contribute to weight loss. One study found that fasting for 24 hours increased metabolic rate by 3.6-14% (7).

 

It is important to remember that daily calorie in/out is the most important factor for weight gain/loss. Without a sustained calorie deficit, fasting itself will do very little for weight or body fat loss. 

3. Benefits of a 24-Hour Fast: Improved insulin sensitivity:

Fasting can lower insulin levels, which improves insulin sensitivity. In one study, fasting for 24 hours reduced insulin levels by 20-31% (8).

 

Improved insulin sensitivity can help with blood sugar control, which is beneficial for people with diabetes. One study found that a 24-hour fast improved glycemic control in people with type 2 diabetes (9).

4. Benefits of a 24-Hour Fast: Improved heart health:

Fasting can reduce inflammation, which is a risk factor for heart disease. In one study, fasting for 24 hours reduced markers of inflammation, such as C-reactive protein (CRP) (10).

 

Fasting can also lower blood pressure and improve cholesterol levels, both of which are beneficial for heart health. One study found that a 24-hour fast reduced blood pressure and improved lipid profiles in healthy adults (11).

5. Benefits of a 24-Hour Fast: Improved brain function:

Fasting can increase brain-derived neurotrophic factor (BDNF), which is a protein that helps improve brain function and protect against neurodegenerative diseases. One study found that fasting for 24 hours increased BDNF levels by up to 400% (12).

 

Fasting can also increase the production of ketones, which can provide an alternative energy source for the brain and improve cognitive function (13).

6. Benefits of a 24-Hour Fast: Increased longevity:

Studies in animals have shown that fasting can extend lifespan (14).

 

Fasting has also been found to promote healthy aging by reducing oxidative stress and inflammation, two processes that contribute to age-related diseases (15).

 

Fasting has also been found to reduce risks of disease, they it can assist with lifespan extension.

7. Benefits of a 24-Hour Fast: Improved immune function:

Fasting can stimulate the immune system by activating immune cells and reducing inflammation (16).

 

Studies have also found that fasting can improve the response to vaccinations (better immune cell production), which suggests that it may enhance immune function (17).

8. Benefits of a 24-Hour Fast: Reduced risk of chronic disease:

Fasting has been associated with a reduced risk of chronic diseases, such as cancer, diabetes, and heart disease (18).

 

The mechanisms behind these benefits are not fully understood, but fasting has been found to improve various metabolic markers and reduce inflammation, both of which are risk factors for chronic diseases.

Safe Ways of Breaking Your Fast:

    1. Drink plenty of water: It’s important to rehydrate after a fast, so start by drinking plenty of water.
    2. Start with a small meal: Begin with a small meal that includes easily digestible foods such as fruits, vegetables, and lean protein. This can help to ease your digestive system back into action.
    3. Chew your food well: Take your time and chew your food well. This can help to stimulate digestive enzymes and aid in the breakdown of food.
    4. Finish with a smoothie: A smoothie can be a great way to end a fast, as it is easy to digest and can provide a boost of nutrients. Choose ingredients that are gentle on the digestive system, such as bananas, berries, and leafy greens.
    5. Do not experiment with new foods: It’s best to avoid trying new or unfamiliar foods after a fast, as your digestive system may be more sensitive than usual. Stick to familiar, easily digestible foods until your body has fully adjusted.

Are there side effects or risks to doing this?

According to the literature, there are potential side effects and risks associated with 24-hour fasting. Some individuals may experience symptoms such as headaches, dizziness, fatigue, and irritability, especially if they are new to fasting or have underlying health conditions (19, 20).

 

Prolonged fasting can also lead to dehydration, electrolyte imbalances, and a decrease in muscle mass (19, 20). It is important to consult with a healthcare professional before starting a fasting regimen, especially if you have a history of medical conditions or are taking medication (20).

You shouldn’t fast if you:

While 24-hour fasting can be a safe and effective way to promote health and weight loss, there are certain individuals who should not fast.

 

 

These include pregnant or breastfeeding women, individuals with a history of eating disorders, those who are underweight or have a BMI below 18.5, and people with certain medical conditions such as diabetes or kidney disease (20). Additionally, children and adolescents should not fast, as they require regular meals for proper growth and development (20).

 

 

If you have any concerns about whether or not fasting is safe for you, it is important to speak with a healthcare professional before starting a fast.

 

I hope you found this guide useful, if so, give it a share on social media!

 

Stay frosty,

Simon

-Nutritionist, Owner of Found My Physique

References

    1. Zauner C, Schneeweiss B, Kranz A, et al. Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine. Am J Clin Nutr. 2000;71(6):1511-1515.
    2. Heilbronn LK, Civitarese AE, Bogacka I, Smith SR, Hulver M, Ravussin E. Glucose tolerance and skeletal muscle gene expression in response to alternate day fasting. Obes Res. 2005;13(3):574-581.
    3. Patterson RE, Sears DD. Metabolic Effects of Intermittent Fasting. Annu Rev Nutr. 2017;37:371-393.
    4. Liang X, Bushman FD, FitzGerald GA. Time-restricted feeding alters the gut microbiome and improves metabolic and cognitive health in mice. Cell Rep. 2015;13(2):1-9.
    5. Narula N, Wong EC, Djukovic A, et al. The effects of time-restricted feeding on gut microbiota and host inflammatory responses. Nutrients. 2021;13(3):823.
    6. Johnson JB, Summer W, Cutler RG, et al. Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radic Biol Med. 2007;42(5):665-674.
    7. Varady KA, Bhutani S, Church EC, Klempel MC. Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults. Am J Clin Nutr. 2009;90(5):1138-1143.
    8. Tinsley GM, La Bounty PM. Effects of intermittent fasting on body composition and clinical health markers in humans. Nutr Rev. 2015;73(10):661-674.
    9. Halberg N, Henriksen M, Söderhamn N, et al. Effect of intermittent fasting and refeeding on insulin action in healthy men. J Appl Physiol. 2005;99(6):2128-2136.
    10. Faris MA, Kacimi S, Al-Kurd RA, et al. Intermittent fasting during Ramadan attenuates proinflammatory cytokines and immune cells in healthy subjects. Nutr Res. 2012;32(12):947-955.
    11. Klempel MC, Kroeger CM, Bhutani S, Trepanowski JF, Varady KA. Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women. Nutr J. 2012;11:98.
    12. Mattson, M. P., Duan, W., & Guo, Z. (2003). Meal size and frequency affect neuronal plasticity and vulnerability to disease: cellular and molecular mechanisms. Journal of neurochemistry, 84(3), 417-431.
    13. Patterson, R. E., & Sears, D. D. (2017). Metabolic effects of intermittent fasting. Annual review of nutrition, 37, 371-393.
    14. Longo VD, Mattson MP. Fasting: molecular mechanisms and clinical applications. Cell Metab. 2014;19(2):181-192.
    15. Johnson JB, Summer W, Cutler RG, et al. Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radic Biol Med. 2007;42(5):665-674.
    16. Li G, Xie C, Lu S, et al. Intermittent fasting promotes bacterial clearance and intestinal IgA production in Salmonella typhimurium-infected mice. Front Immunol. 2018;9:2473.
    17. Dhabhar FS, McEwen BS. Enhancing versus suppressive effects of stress hormones on skin immune function. Proc Natl Acad Sci U S A. 1997;94(15):7462-7467.
    18. Horne BD, Muhlestein JB, Lappé DL, et al. Randomized cross-over trial of short-term water-only fasting: metabolic and cardiovascular consequences. Nutr Metab Cardiovasc Dis. 2013;23(11):1050-1057.
    19. Patterson, R. E., & Sears, D. D. (2017). Metabolic Effects of Intermittent Fasting. Annual Review of Nutrition, 37, 371-393.
    20. Anton, S. D., Moehl, K., Donahoo, W. T., Marosi, K., Lee, S. A., Mainous, A. G., … & Mattson, M. P. (2018). Flipping the metabolic switch: Understanding and applying the health benefits of fasting. Obesity, 26(2), 254-268.
Categories: Health & Wellbeing