Is Fasting Healthy

What is fasting?

Fasting involves going without food or drink for a decided window of time. Individuals engage in this practice for several reasons. These include religious, medical, ritualistic, or ethical. Fasting may be partial or complete, short or long, and most times it depends on the individual’s capacity or the reason why the person is fasting.1 Numerous religions encourage fasting and for many centuries, it has been a practice recommended by doctors and other medical practitioners. This is due to emerging evidence suggesting various health benefits in specific individuals. 

Benefits of fasting

There are several health-related benefits linked to fasting which include:

  1. Maintaining healthy blood sugar levels: Some existing research supports fasting as a way to improve blood sugar control and potentially lower the risk of diabetes. Current studies show that intermittent and alternate-day fasting helps to lower the risk of developing type 2 diabetes2
  2. Fasting allows your digestive system to rest: This can boost your metabolism, allowing you to burn calories more efficiently. Poor digestion can impair your ability to metabolize food and burn fat. Intermittent fasting can improve metabolic function by regulating digestion and promoting healthy bowel function.3 During periods of fasting, the body switches from burning carbohydrates as the main source of fuel to fats
  3. Fasting is shown to have beneficial effects on those suffering from depression: An antidepressant effect is present because it increases the availability of feel-good neurotransmitters like serotonin, and other happy hormones that are naturally produced in your brain. Fasting and calorie restriction alleviate negative emotions such as tension and anger, while also increasing feelings of happiness. 
  4. Helps fight inflammation: Inflammation is a natural process in the body that helps damaged cells heal. However, inflammation may play a role in the development of chronic conditions such as heart disease, cancer, and rheumatoid arthritis. In some studies, fasting is shown to help reduce inflammation and promote better health4
  5. Fasting may help reduce the chances of developing heart disease: Cardiac diseases have become increasingly common causing a quarter of all deaths in the UK. Fasting is an effective way of adjusting diet and lifestyle to manage or prevent the onset of heart diseases. Some studies show that alternate-day fasting can help reduce cholesterol levels in the body, commonly linked to the development of cardiovascular diseases
  6. Fasting helps regulate the hunger hormones (e.g., Ghrelin) in the body: When you abstain from eating, it helps your body properly digest the food that has been previously consumed. Thus, allowing hunger hormones to accurately detect when that person is hungry. Consider fasting to be a reset button: the longer you fast, the more your body can regulate itself to release suitable hormones, allowing you to experience true hunger. Not to mention, when your hormones are functioning properly, you feel fuller faster,  preventing overeating3

How often should you fast?

The decision to fast and fasting frequency depends on individual strengths and preferences. Additionally, it depends on the motivations, which could be medical or religious. Therefore, sometimes the fasting approach depends on the reason. 

The three popular approaches to intermittent fasting are: 

  • Alternate day fasting

Eat a normal, healthy diet one day and then fast or eat only one small meal the next. The small meal is usually less than 500 calories.

  • 5-2 fasting

Eat normally five days a week and fast twice a week.

  • Daily fasting with time constraints (i.e. intermittent fasting)

Eat normally every day, but only during an eight-hour window. For instance, skip breakfast but eat lunch at 11 a.m. and dinner by 7 p.m. 

Skipping meals is not advised for those under the age of 18, those with a history of disordered eating, or those who are pregnant or breastfeeding. Similarly, Athletes may struggle to properly fuel and refuel for an active lifestyle. If you have diabetes or other medical conditions, consult your doctor before considering fasting. An important thing to note is that our bodies are different and the same method may not apply to everyone. Hence, you should always check with your doctor or medical professional, so that you can be sure of what approach would work best for you.5

Does fasting detoxify the body?

This is a pretty controversial topic. Many specialists would argue that fasting does detoxify the body, and contrastingly others would say it does not cleanse the body. However, I would like to agree that the body has mechanisms that are designed to carry out the detoxification process naturally. Therefore, trying to achieve this by excessive fasting may be counterproductive. There is no scientific evidence that fasting can help detoxify the body. Furthermore, fasting for an extended period without proper knowledge can be dangerous to your health.6

Drinking sufficient water and a healthy diet is often enough to promote your body’s natural detoxification process, so you do not necessarily need to fast to help your body work better. Rather than restricting your intake of food generally, you may want to help your body by doing the following things, recommended by Dr. Hopkins

  • Limit your alcohol consumption to one or two drinks per day; gradually cutting it off entirely
  • Limit your caffeine intake avoiding jitters, sleeplessness, or heartburn
  • Replace processed foods with fresh, natural products
  • Reduce or eliminate the consumption of processed sugar. This may seem difficult at first but you can start with some sugar detox diets 

Spiritual and religious fasting

Fasting is a discipline recommended by many religions to increase faith and allow for deeper introspection, amongst other benefits. The length and frequency varies, depending on the religion. 

Medical reasons for fasting

It has been established that fasting can be done for medical reasons, these include: 

Disadvantages of fasting

  1. May encourage overeating: Intermittent fasting is set up in a way that you fast for most of the day and eat within a specific time window. Some people, having deprived themselves of food the whole day, may try to indulge in as much food as possible, therefore making the body work extra hard to process that food. This certainly defeats the purpose of the fast
  2. May lead to eating disorders: Intermittent fasting restricts eating showing a direct correlation between not eating at all and weight loss. The more/longer you fast, the more calories you will avoid and the more weight you will be able to lose. If you have previously struggled with an eating disorder, fasting may cause you to relapse or develop a new eating disorder. After all, any diet that encourages skipping meals can result in some negative food relationships7
  3. Long-term effects of fasting: Fasting can harm not only the immune system but also many of the body's organs, including the liver and kidneys. Fasting may impair vital bodily functions. Abstaining from eating could also be dangerous for people who are already malnourished. Fasting can even lead to death if the body's stored energy source is completely depleted8


Fasting is positive, for a variety of reasons but as with all things, it should be done with full knowledge of what it is about and the expectations from it. Many people fast for spiritual or religious reasons, and some for medical reasons, all of which have great benefits for the mind, soul, and body. However, before deciding to fast, you should check with your doctor or other medical professional, so that you can be properly informed on how to go about your individual fast. 


  1. Fasting | definition, description, types, benefits, & facts | britannica [Internet]. [cited 2022 Dec 7]. Available from:
  2. Top 5 health benefits of fasting [Internet]. BBC Good Food. [cited 2022 Dec 7]. Available from:
  3. 10 benefits of fasting that will surprise you [Internet]. Lifehack. 2014 [cited 2022 Dec 9]. Available from:
  4. Furman D, Campisi J, Verdin E, Carrera-Bastos P, Targ S, Franceschi C, et al. Chronic inflammation in the etiology of disease across the life span. Nat Med [Internet]. 2019 Dec [cited 2022 Dec 9];25(12):1822–32. Available from:
  5. When to fast, 3 different types of fasts, and their benefits [Internet]. [cited 2022 Dec 9]. Available from: 
  6. Word of caution. The Times of India [Internet]. [cited 2022 Dec 9]; Available from:
  7. The pros and cons of fasting [Internet]. [cited 2022 Dec 9]. Available from: 
  8. The disadvantages of fasting [Internet]. Healthy Eating | SF Gate. [cited 2022 Dec 9]. Available from:
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Toluwanimi Ojeniyi

Master of Science - MS, Global Health, University of Ibadan, Nigeria

Toluwanimi is a Public Health specialist with experience in programs administration and health insurance. She is currently undertaking a Masters in Global Health at the University of Ibadan.
She is a skilled health educator and health writer. In her free time, she reads and volunteers.

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