The chances are you have already heard of the term “intermittent fasting”. Fasting is not a new idea – people have fasted for thousands of years, for both health and spiritual reasons. But what exactly is intermittent fasting, and why might it be beneficial for you?
What is Intermittent Fasting?
Intermittent fasting has gained huge popularity over the last few years. While people may choose to fast for many different reasons, intermittent fasting is most commonly used as an alternative to more traditional diets to lose weight.
Unlike other fasts, during which you may limit the type of food you consume (like juice fasts) or eat no food at all (water fasts) for a period of time ranging from 24 hours to several days, intermittent fasts are different. Intermittent fasting programs do not limit the type of food you eat.
When you are intermittent fasting, you are simply limiting your eating time to a restricted number of hours within the day. Depending on the type of intermittent fast you choose, you may eat nothing at all during fasting hours (only drinking water) or you may restrict your calories to a strictly limited number.
Most people fast daily for a period of 8-12 hours anyway, overnight, while they are asleep. Intermittent fasting increases this period to 16 hours or longer.
This may seem a little complicated, but it will all start to make sense when you look at some of the different types of intermittent fasting, as outlined below.
Types of Intermittent Fasting
There are several different versions of intermittent fasting, but the two most common and popular are the 16:8 protocol, and the 5:2 protocol.
The 16:8 protocol is one of the most popular types of fasting program to follow, probably because it requires the least amount of change to your normal routine. The method was popularised by Martin Berkhan on the website leangains.com
As most people normally fast for up to 12 hours overnight anyway, this protocol simply requires extending the fasting period by skipping breakfast and not eating after dinner.
You can set up the eating pattern in any way that suits you. The only rule is, out of every 24 hours, 16 of those should be fasting hours, and you can eat as normal during the remaining 8 hours. If you don’t feel hungry in the morning and prefer to skip breakfast, it makes sense to start your eating window around 12pm and start fasting around 8pm. However if you need to eat in the morning to function properly, you can eat breakfast as normal around 8am, and eat the last meal of the day at around 4pm.
During the eating window, you can eat what you want, with no calorie restriction (although there is further nutritional advice for those in training or trying to achieve specific outcomes). During the fasting period you can drink water but should consume no calories in the form of drinks or otherwise.
The 5:2 diet was popularised by Dr Michael Mosely in a BBC documentary, and later as a bestselling diet book.
Rather than splitting your day into fasting hours and non-fasting hours, the 5:2 protocol splits your week into fasting days and non-fasting days.
You choose two 24-hour periods each week in which to fast. During these fasting periods you can eat, but your calories for the day are strictly limited to 500 for women and 600 for men.
On non-fasting days there are no calorie limits or diet restrictions. Participants are encouraged to eat “normally”, but not to binge or overeat.
The Pros and Cons of Fasting
Of course people wouldn’t bother with these methods unless there were some advantages. So what are the benefits of intermittent fasting?
- Weight loss – the main reason that most people undertake an intermittent fasting plan is to lose weight, and studies show that this way of eating can indeed be a very effective way to lose fat, not just water weight.
- Flexibility – one of the big reasons that people give up on standard diets is that they find it difficult to live and enjoy their normal lives on a restricted diet. This feeling of being constantly deprived means that most people will eventually run out of willpower when they are tempted by a piece of birthday cake or invited to a dinner out with friends. The beauty of intermittent fasting is that you can eat as you wish during non-fasting periods, and you can usually adjust your fasting times around your life. You can literally have your cake and eat it!
- Simplicity–there is no need to count carbs or balance your macros when you are intermittent fasting, and many plans don’t even require calorie counting either. You simply eat when it is time and don’t eat (or eat very little) when you are fasting.
- Health benefits–several scientific studies have shown that intermittent fasting offers health benefits that go beyond weight loss. These include reducing chronic inflammation, improving insulin sensitivity, and reducing blood cholesterol levels.
However, like many diets, following intermittent fasting does come with its downsides. These include:
- Lack of guidance – if you are overeating during non-fasting periods, you may not lose weight despite fasting. There is also little guidance on the type of foods you should eat while intermittent fasting, and an unhealthy diet will cancel out any positive health benefits you may gain from the program.
- Long periods without food– some people may find it difficult to fast, or that it triggers them to binge eat at the end of the fasting period. For this reason, intermittent fasting is not suitable for people who have suffered from an eating disorder.
- Low mood and energy due to low blood sugar – if you get “hangry”, or find it hard to concentrate when you have gone too long without eating, you might find fasting hard going. However, a 12-week study showed that this way of eating did not impact exercise ability or performance.
- Not suitable for people with some medical conditions– if you have diabetes and need to maintain blood sugar levels, fasting could be dangerous. You also shouldn’t fast if you are pregnant, and fasting may impact your fertility if you are trying to get pregnant.
Many people have found intermittent fasting to be an easy and effective way of losing weight, and it is worth a try if you struggle with the restrictiveness of other diet programs. However, you must remember that there is nothing magic about this diet – it works simply by reducing your calorie intake in the long-term. If you are consuming excess calories when you are not fasting, or you feel compelled to binge when you stop fasting, this probably is not the diet plan for you.