Fasting has become the new buzzword in health and dieting, enjoying extensive coverage in the national press, on TV and in many books. Traditionally, fasting has been thought of as a long, arduous process requiring huge amounts of willpower, however a new breed of fasting, called intermittent fasting, has emerged and is 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?
The Benefits of Fasting
Fasting can enhance an already healthy lifestyle, and brings health benefits such as weight loss, improved insulin levels and lower inflammatory markers. Fasting can even reduce seizures, promote longevity, and lower someone’s risk of cancer, Alzheimer’s disease and diabetes. 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. Autophagy is like a spring clean for the body, 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. Another mechanisms behind intermittent fasting’s ability to promote health is that it causes positive stress in the body, and this mild stress that it creates improves the body’s ability to adapt to stress and protect against disease.
Some studies suggest that intermittent fasting is at least as effective as low calorie diets for weight loss, and easier to stick to
When You Shouldn’t Fast
It is not advised for females to fast during pregnancy, breastfeeding or their periods. If you know that you suffer from a blood sugar imbalance, chronic 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, whereas eating regular meals is likely to be a better approach in such cases. If you currently, or ever have, suffered from an eating disorder then food restriction of any kind is not recommended. And finally, growing children 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 those suffering from autoimmune conditions (like rheumatoid arthritis, lupus, psoriasis and Hashimoto’s disease) don’t benefit from intermittent fasting in the same way, because the autophagy process may not be taking place to the same extent.
The bottom line is fasting shouldn’t make you feel bad – if fasting leaves you feeling very hungry, moody, unable to concentrate, stressed, fatigued or leads to trouble sleeping, then you should stop fasting and go back to eating more regular meals.
It is not advised for females to fast during pregnancy, breastfeeding or their periods
Types of Intermittent Fasting
There are various types of intermittent fasting practised across the world, here is a brief overview of the most popular types:
|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 5:2 fast|
|This is the type of intermittent fasting made popular by Michael Mosley on the Horizon programme: Eat, Fast, Live Longer. 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 little guidance about what to eat 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 it.
This fasting period commonly 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, after a long fast, there seems to be an exaggerated drop in autophagy when eating is resumed during which time pathogens are free to multiply. This tells us that we want to fast for less than 24 hours to benefit from the maximum immune boosting powers of autophagy and reduce the period of immune suppression at the end of the fast.
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.
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. Speak to your GP to check suitability if you are on medication or have any serious health problems, and wait until your stress and blood sugar are under control before you begin. Then go slowly – start with one day a week, and then increase the frequency gradually as and when you feel ready.