first hit the headlines back in 2013 , and has been popular ever since. Based on the idea that fasting intermittently delivers health benefits, including weight loss , these days there’s more than one way to do it, and they all come complete with pros and cons.
Here’s some need-to-know info about 3 intermittent fasting (IF) styles.
1. The twice-a-week method
The most popular one of these is the 5:2 diet, which prescribes eating normally five days a week, while fasting for the other two.
On this particular IF diet, the twice-weekly fasting days shouldn’t be consecutive, and when they roll around, you eat a quarter of your usual food intake, which for most people means restricting yourself to about 2000 kilojoules a day .
The weight-loss results
: The most recent research shows that the 5:2 diet delivers similar weight-loss results as following a daily kilojoule-restricted diet .
: The fact that you get a break between fasting days, and that there’s only two of them a week, may make this style of IF easier to stick to than some others. You can also be flexible about which days you fast, week to week, which may also make 5:2 more liveable than other IF methods.
Plus, unlike some IF diets, you can spend your 2000 fasting-day kilojoules in whatever way works for you, whether that’s in one single meal or in smaller meals throughout the day .
Like all IF diets, some people may be tempted to overdo it when they’re not fasting, although to date research shows this doesn’t tend to happen, or at least not to an extent that prevents weight loss .
Experts have also raised concerns that, in focusing purely on kilojoule restriction, the 5:2 diet – or any IF diet – doesn’t place emphasis on the types of foods eaten, or help people understand which foods are healthier choices and how to eat more of them .
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2. The every-other-day method
With this type of IF, you fast one day, eat normally the next, and repeat. There are a couple of different ways to do it – some methods allow you to eat up to 2000 kilojoules a day on fast days, while other alternate-day fasting diets require fast days to be no-food zones.
The weight-loss results:
According to a 2017 study
that compared alternate-day fasting to standard kilojoule-restriction diets, the diets produced very similar weight-loss results .
Like 5:2, supporters of alternate-day fasting say the break between fasting days can make this diet easier to stick to than those that require daily kilojoule restriction .
According to the 2017 study, the opposite may actually be true – more people dropped out of the alternate-day fasting diet than the daily kilojoule-restricted one, because they were dissatisfied with it
Because every second day needs to be a fast day, regardless of lifestyle or social commitments, this style of fasting may not be as liveable as others, which may explain the higher dropout rate .
Plus, the same study also found that six months after stopping the diet, alternate-day fasters had elevated levels of cholesterol .
3. Time-restricted eating
This involves fasting for a certain amount of time every day, then eating whatever you like during the other ‘window’.
One of the most popular ways of doing this is the 16:8 diet: fasting for 16 continuous hours, then being free to eat during the other eight, with 10am-6pm the most widely prescribed ‘eating window’ .
The weight-loss results: A study published in 2018
found that people following the 16:8 diet lost three per cent of their body weight in just 12 weeks, because they ate 1400 fewer kilojoules a day, without having to count them .
So far, research suggests that time-restricted eating plans, such as 16:8 may be easier to stick with than other types of IF, perhaps because you can avoid becoming overly hungry .
Not being able to eat after 6pm every single day may restrict your social and family life. And while you might be tempted to simply delay your eating window when you need to, experts warn against it for best results.