Intermittent fasting (IF) has been a hot topic for a while now. First came the 5:2, then the 16:8, not forgetting the many trends like Keto, Paleo and so on. Naturally, there are pros and cons to each diet as each person is different – so there's no 'one size fits all' approach. However, IF is more than just about weight loss. Here are the benefits, pros and cons of intermittent fasting you should know that go way above and beyond changing the size of your waist and losing weight.

What is intermittent fasting?

Intermittent fasting is an eating pattern where you cycle between periods of eating and fasting. It's not specific to which foods you eat, rather when you should eat them. There are several different intermittent fasting methods, all of which split the day or week into eating periods and fasting periods. No food is allowed during the fasting period, but you can drink water, coffee or tea.

Checking in or working alongside a Certified and Registered Nutritionist or Dietitian is important as not only can they help you understand how to reach your health goals on a daily basis with solutions and plan food choices, they assess your personal health and help you to prevent disease – particularly if you have a strong family history of heart disease, neurodegenerative disorders, cancer and diabetes, for example.

health benefits of intermittent fasting and the 5 2 diet

Pros of intermittent fasting: the benefits

1. You may prevent disease 

Fasting promotes longevity by reprogramming metabolic and stress resistance pathways, so with IF, you can potentially reduce your risks of many serious diseases and conditions including heart disease, diabetes and even cancer (1). This happens in part because fasting helps our fat cells adapt and metabolise more efficiently, which has a massive impact on our chances of developing obesity and type 2 diabetes. 

2. You can give your immune system a BIG boost

Fasting may help to switch on a process which can help get rid of old redundant cells in the body and create new stem cells which can have transformative effects on our immune systems and possibly even reduce our chances of developing certain cancers (2).

3. You can develop better brain health

Intermittent fasting can really help brain health and possibly even prevent some neurodegenerative disorders such as Parkinsons and Alzheimers. In fact, research today clearly shows that lifelong diet and lifestyle interventions that retard ageing processes, and thereby reduce risk of disease, may be of great value (3).

4. You may be able to de-stress 

One of the main scientific explanations of why our bodies respond so well to intermittent fasting is to do with the biological process called, 'hormesis'. In essence, when our bodies are exposed to little stress or toxin (while a large dose of the same stress or toxin could be very detrimental), they get stronger from the process of hormesis and actually help us to stay more youthful, energised and switched on (4).

For example, hormesis means that a small amount of stress can actually activate other ‘anti-stress’ pathways that can help us cope better with stress in general. However, if we were inundated with high amounts of stress, it could actually kill these neutrons instead. This process helps account for the long-lasting benefits of IF many of can experience in their day to day lives.

side effects of intermittent fasting and why it can be bad

Cons of intermittent fasting: the downside

Of course, we’re all completely different so it makes sense that we all need to find a way of eating, living and feeling that is just right for us, and intermittent fasting is not necessarily the right fit for everyone:

1. Your fertility may be affected

There is a chance that IF may affect future fertility in women. However, there is no hard and fast evidence to show that it is or is not problematic – there is simply not enough rigorous human studies on intermittent fasting to show the potential impact on reproduction and fertility, if any, as a result of long-term intermittent fasting, so this is something to be mindful of (5).

2. You may become more stressed

While small amounts of stress should promote repair in your body, for people experiencing very high levels of stress in their daily lives, the 5:2 might not be advisable because skipping meals might increase the experience of stress. Common sense should tell you that if you start feeling unwell at all, then you should stop intermittent fasting immediately.

3. Do not try IF if you have/have had an eating disorder

Totally avoid intermittent fasting if you have a history or any sort of eating disorder or inclination towards disordered eating, are very lean or are already underweight. The combination of fasting and increased cortisol (the stress hormone) can heighten obsessive thoughts about food. If you relate to this, following rules and restrictions involved in 5:2 or intermittent fasting is definitely not for you (6).

4. Do not try IF if you are any of the following

There are certain people who shouldn’t consider fasting in any form. These include children, type 1 diabetics, diabetics using insulin and anyone who is pregnant or thinking about trying to conceive or is breastfeeding. These people should be following government guidelines and reaching their daily required nutrients and definitely not restricting their calories, for obvious reasons (7).

Part of following the 5:2 programme is about calorie restriction, so calorie counting apps can be useful to track the food you choose to eat during the two fast days. As stated above though, if you have a history of eating disorders or disordered eating, then these kind of calorie counting apps are not advisable. Make sure you are aware of what you're getting into before you try any new eating regimen and always seek the help of a medical professional at the first sign of any issues.

READ NEXT: Tried and tested remedies and products to help you manage weight loss.

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From how it affects your fertility to your heart, discover a Nutritionist's guide to the pros and cons of intermittent fasting that go beyond weight loss.


6,7. Dr Michael Mosley, Mimi Spencer, The Fast Diet, 2014

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