With studies suggesting fasting may boost health, promote longevity and keep those extra pounds at bay, registered nutritionist Kerry Torrens takes a look at the science behind the claims and how fasting might fit in to our modern lifestyles.


What is fasting?

When we refer to ‘fasting’ we’re talking about the abstinence from all or some food and drink for a given period of time. Despite being popularised by today’s diet world, the practice of fasting dates back centuries and is thought to be one of the oldest therapies in medicine. Whether it involves refraining from food and drink or a lighter, lower-calorie form of eating, many argue that going without food for periods of time is something our bodies are suited to.

You may also see the practice referred to as ‘intermittent fasting’ or ‘time restricted eating’; both these terms suggest eating patterns that expand the amount of time your body is in a fasted state. This state is achieved by reducing your ‘eating window,’ or the time during which you eat.

Discover our full range of health benefit guides and learn more about different types of fasting, such as the 5:2 diet, intermittent fasting and the fast 800 diet.

Read on to discover the benefits of fasting:

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  • Influences your metabolism
  • helps with weight management
  • supports blood sugar levels
  • improves gut health
  • supports heart health
  • helps prevent diseases
  • helps delay ageing
  • supports your circadian rhythm
  • aids brain health
  • helps reduce anxiety

Top 10 health benefits of fasting

1. Supports hormones and genes that influence metabolism

When you haven’t eaten for a while, your body adapts via a change in hormone levels to make stored body fat more accessible and to initiate repair processes. There is also a shift in gene expression which increases the ability of your muscles to use fats.

2. May support weight loss

Studies show that controlling the times we eat – or undertaking short-term fasts – may aid weight reduction, fat loss and improve blood lipids.

3. Supports blood sugar management

Several studies support the use of fasting as a means of improving blood sugar control and potentially reducing the risk of diabetes, although gender may play a part and more studies are needed.

For those with type 2 diabetes, intermittent fasting benefits include decreasing fasting glucose and fasting insulin, reducing insulin resistance and decreasing levels of the appetite hormone, leptin.

4. Supports gut health

Studies suggest another benefit of fasting is its positive impact on both the diversity and number of beneficial bacteria in the gut. This appears to have a beneficial effect on weight change, waist measurement and metabolism.

5. Supports heart health

Studies suggest that intermittent fasting may reduce some of the risk factors for heart disease – including blood pressure, cholesterol and markers of inflammation.

6. May help disease prevention

Lightening your normal eating pattern appears to give your body the time to focus on other important functions, including disease prevention. This is because, when we fast, the body initiates a process called autophagy. This is likened to the body’s ‘house-keeping’, when waste materials from cells are removed.

Autophagy is thought to improve the body’s ability to manage chronic inflammation and, as such, reduce the risk of conditions such as heart disease, multiple sclerosis and rheumatoid arthritis.

7. May delay ageing and support growth and metabolism

Fasting, and in particular adopting a diet low in protein, has been associated with an extended life expectancy in animal studies.

Fasting appears to promote levels of human growth hormone, a hormone that plays an important role in growth and repair, metabolism, weight loss, muscle strength and exercise performance.

Current longevity research is largely limited to animals, so more studies are needed to fully understand how this may impact human ageing.

8. May reset your circadian rhythm

Studies suggest that intermittent fasting directly influences the gut microbiome and this in turn leads to changes in the levels of chemicals called metabolites that act as signalling molecules to our central body clock. In this way, fasting may help reset our circadian rhythm and benefit conditions like obesity that are associated with a disordered body clock.

9. May support brain function

Studies in animals suggest fasting may protect against and improve outcomes in Parkinson’s and Alzheimer’s, as well as improve brain function by supporting memory and brain processing. Similarly, animal studies suggest fasting may protect brain health and increase the production of nerve cells.

More research is needed to determine the relevance for humans and whether age and bodyweight, as well as the intake of specific nutrients, may outweigh fasting.

10. May reduce anxiety

Human studies report fasting may reduce symptoms of anxiety and depression and improve social connection. More studies are needed to assess these effects but findings to date are encouraging.

Plate with a knife and fork and an alarm clock

Is fasting safe for everyone?

Fasting is not for everyone. It’s advisable to speak to your GP or healthcare professional before starting a new dietary regime, especially if you’re under 18, elderly, have a pre-existing medical condition (including diabetes, high blood pressure, kidney stones or acid reflux) or are on medication. Fasting isn’t recommended for people who are underweight, have or are recovering from an eating disorder or are pregnant or breastfeeding.

For women of reproductive age, the timing of a fast may be best performed during the follicular (early) stage of the menstrual cycle.

Should I consider intermittent fasting?

Studies in humans suggest that fasting is safe and effective for most people, but probably no more effective, from a weight-loss perspective, than other forms of dieting.

If you do decide to give fasting a go, do so by limiting the hours of the day when you eat and ideally eat earlier rather than later (aim to eat during the first 6-8 hours after waking). Don’t forget both the quantity and quality of the food you eat during your eating window are crucial – so aim for a varied, balanced diet that includes wholegrains, fruit, vegetables and a variety of lean proteins.

Please note: if you’re considering any form of diet, please consult your GP first to ensure you can do so without risk to your health.

Read more of our health guides:

What is the 5:2 diet?
What is an intermittent fasting diet?
What is the Fast 800 diet?
What is the Pioppi diet?
What is a ketogenic diet?

This article was reviewed on 23 June 2023 by Kerry Torrens, Registered Nutritionist.

Kerry Torrens is a qualified Nutritionist (MBANT) with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including Good Food.

All health content on goodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. If you have any concerns about your general health, you should contact your local health care provider. See our website terms and conditions for more information.


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