Once upon a time, fasting was considered an extreme, arduous dietary strategy reserved for health nuts or those taking part in specific religious or cultural festivals, requiring huge amounts of willpower. How times have changed...
These days, a new breed of fasting has emerged, known as intermittent fasting, and thanks to extensive coverage in the media almost everyone has heard of it. In fact it's fast becoming the most popular way to lose weight and stay younger for longer.
Some studies suggest that intermittent fasting is at least as effective as low calorie diets for weight loss, and easier to stick to. So, you may be wondering, should I try fasting and if so, how do I do it?
Why should I try fasting?
There are lots of emerging reasons why fasting may be worth considering in the pursuit of health, wellbeing and longevity. According to experts, it can enhance an already healthy lifestyle, bringing health benefits such as improved digestion, fat burning, weight loss and improved insulin levels, as well as being therapeutically appropriate for many of those suffering from any of the metabolic syndrome family of conditions such as diabetes, heart disease and obesity. Fasting can even reduce seizures and lower risk of cancer, depression, Parkinson's and Alzheimer’s disease.
There are various explanations as to why and how fasting brings about such health benefits. One possibility is a ‘clean-up’ process called autophagy, which is a sophisticated immune defence mechanism that occurs during times of food deprivation. You can think of autophagy as your body's way of pruning the dead areas of the garden, or spring cleaning the house. This process is capable of destroying pathogens inside cells, plus it can seek out and find pathogens hiding in inaccessible locations, and provide immune surveillance to help detect the presence of foreign pathogens. All good things when it comes to disease prevention and extending lifespan.
Giving your digestive system an extended break from dealing with food can be a stark and welcome contrast to the constant grazing may of us are used to. This hiatus from taking in extra fuel not only promotes the burning of our own fat stores for energy, but may also leave your digestive system calmer, favourably altering the bacterial balance in the gut to reduce localised inflammation.
Another mechanism behind intermittent fasting’s ability to promote health is that it causes positive stress in the body, known as hormesis. This seemingly beneficial, mild stress that it creates improves neural plasticity and disease resistance, as well as boosting the body’s ability to adapt to the more harmful stress most of us encounter from time to time.
When you shouldn’t fast
After reading about all the benefits, you may be ready to dive in and give it a try. But not so fast! While fasting can improve health, the truth is that it's not necessarily suitable or safe for everyone, at least not until you've made some changes to get you ready and increase your chances of success.
First and foremost, it's not advisable for females to fast during pregnancy, breastfeeding or during their menstrual periods.
Secondly, if you know that you suffer from a chronic blood sugar imbalance, unresolved stress, adrenal or thyroid problems, then fasting may not be a good idea because restricting food intake can elevate stress hormones and worsen these conditions. In such cases, fasting may be something to work towards, after cleaning up your diet and improving other lifestyle factors first. Working with a qualified nutritional therapist or functional medicine specialist is a good place to start.
Thirdly, if you currently suffer from any kind of disordered eating, or ever have done, then food restriction of any kind is not recommended.
And finally, fasting isn't going to be a good idea in most cases for growing children, who have different nutritional needs to adults and should eat regularly to provide the steady fuel necessary for physical and cognitive growth and development.
Additionally, it has been found that autophagy may not take place to the same extent in those suffering from autoimmune conditions (like rheumatoid arthritis, lupus, psoriasis and Hashimoto’s disease), and therefore these individuals may not benefit from intermittent fasting in the same way.
The bottom line is fasting shouldn’t make you feel bad – if fasting leaves you feeling very hungry, moody, unable to concentrate, stressed, dizzy, fatigued or leads to trouble sleeping, then you should stop fasting and go back to eating more regular meals.
Types of intermittent fasting There are various types of intermittent fasting you may want to try, here is a brief overview of the most popular types...
The 5:2 fast: This is the type of intermittent fasting made popular by Michael Mosley on the Horizon programme: Eat, Fast, Live Longer, and has now become the focus of many popular books. You limit calories drastically (around 500 calories) on two days per week (each fast lasting a full 24 hours), and eat whatever you like on the other days. It suits some people well, and many report easy and rapid weight loss, mental clarity and improved health. It should be noted, however, that this type of intermittent fasting doesn’t suit everyone and can be hard on the body. There is also the tendency for an 'anything goes' approach on non-fast days, with some followers feeling that they can stuff themselves with whatever they like which can become problematic for long-term health. Additionally, this type of fasting is more likely to be detrimental to health if your blood sugar is unstable or you are suffering from stress, fatigue, thyroid or adrenal problems.
The overnight fast: this is my favourite type of intermittent fasting, especially for beginners. Extending the time period between dinner and breakfast allows the digestive system a chance to rest, and encourages fat burning, as well as promoting good health and longevity. It’s easy to do and requires minimal willpower because you are asleep for most of the fasting period. The fasting window typically lasts between 14 – 16 hours, effectively reducing the time frame within which to eat to 8 or 10 hours per day. You begin fasting at the end of dinner and break the fast when you eat the following day, allowing you to adjust your meal timings to suit your lifestyle. This type of shorter, overnight fasting is effective because autophagy is not up-regulated by long fasts, in fact, research has shown that we want to fast for less than 24 hours to benefit from the maximum immune boosting powers of autophagy. Another reason that overnight fasting is the best option to choose is that autophagy appears to follow a diurnal rhythm, which is coordinated with the circadian clock, suggesting that we should primarily fast overnight rather than during the daytime. There is some evidence to suggest that women do better fasting for 14, rather than 16 hours, and this is certainly a good place for everyone to start. This type of fasting is easy to start gently and build up gradually, enabling followers to keep a close eye on their health and any symptoms that may occur.
Alternate day fasting: As the name suggests, you follow a pattern of severe calorie restriction on one day (around 400 calories) and then you eat freely the next. This type of intermittent fasting is fairly extreme and therefore hard to stick to – in fact research suggests that many participants following this regime became so hungry on feast days and ate so much that they failed to lose any weight. This type of severe calorie restriction would not be my recommended type to try in most cases.
The golden rule with any type of dietary change, especially intermittent fasting, is to listen to your body and don’t be rigid about your routine. If you wake up and feel that you don’t want to miss a meal, then don’t. I also recommend that you take the time to work on your stress, sleep and blood sugar if you need to before you give it a go. Then start slowly - try one day a week, and then increase the frequency gradually as and when you feel ready.
Speak to your GP to check suitability if you are on medication or have any serious health problems.