5 intermittent fasting methods - and what they entail

If proof were needed that Britain is fast becoming one of the fattest nations in the western world, Cancer Research UK has revealed that more than 42 million adults (71%) in the UK will be classed as ‘overweight’ or ‘obese’ by the year 2040.

It’s an eye-opening statistic that shows just how the nation’s weight gain is fast becoming an epidemic and while it's an issue that many argue the government needs to help solve there are certainly steps individuals can take.

Traditional diets are rarely the long-term answer to reaching a sensible and sustainable weight which is why the idea of intermittent fasting has caught on in recent years. After all, it offers opportunities to have some semblance of a normal eating routine.

“The body stores food energy, or calories, in the form of glucose and fat. If you’re eating, you cannot burn stored food energy, because your body wants to store it,” Dr Jason Fung, one of the world’s leading experts on intermittent fasting and the author of the best-selling book The Complete Guide To Fasting, explains.

“Only when you don't eat, or fast, do you give the signal for the body to release its stores of glucose and fat.”

Read more: 10 expert-approved weight loss tips good for your body and mind

Fasting’s appeal lies in its simplicity and, for men particularly, it represents a more manageable way to lose weight. It’s also less awkward than telling everyone that you’re ‘on a diet’.

Men are more likely to benefit from fasting than women. As men possess more muscle, on average, than women, they are also likely to lose weight more rapidly.

It’s also been proved that incorporating some resistance exercise into your fasting routine before you eat in the morning can also help to maximise results.

As well as helping to reset your relationship with food and helping you to identify genuine hunger signals, fasting can also give your body a much-needed spring clean. When your body has been without food for 12 hours or more, a process called ‘authophagy’ begins whereby damaged or old cells are removed to make way for new ones. It’s one of the reasons why scientists believe fasting can also make you feel sharper and more productive.

Research by the National Institute on Health, for example, has shown that reducing your calorific intake for two days a week helps to boost the levels brain-derived neurotrophic factor (BDNF) in the brain, the hormone that acts like a fertiliser on brain cells, helping to encourage not just survival but growth of cells too.

Read more: A man's guide to doing battle with belly fat

If you’re contemplating fasting then it’s important that you don’t embark on anything too extreme.

“Start slowly by eating three meals a day with no snacks. Then you can try to drop a meal, and gradually continue experimenting to see what works best for you,” adds Dr Fung. “All intermittent fasts will work but longer ones to be more powerful, but shorter, more frequent fasts can be just as good. It's an individual preference.”

Watch: Want to lose weight? Try intermittent fasting

Five types of intermittent fasting

1. The 16:8 method

Sometimes called the ‘Leangains diet’, the 16:8 method involves fasting for 16 hours each day, leaving just an eight-hour window in which to eat. Typically, people on this fast usually finish their evening meal by 7pm or 8pm and then skip breakfast the following day before having lunch as normal.

One 2012 study found that limiting the feeding window of mice to an eight-hour period each day made them less prone to obesity, diabetes and liver disease, even if they ate the same amount as mice that were allowed to eat whenever they chose.

And it works on mice and men. When the Prime Minister, Boris Johnson, came out of hospital after his COVID scare in April, 2020, he said his inability to deal with the virus was down to his excess weight and set about losing it. After shedding two stones, he attributed his success to the work of his personal trainer Harry Jameson who is an advocate of the 16:8 diet.

2. The 5/2 method

Favoured by the likes of TV presenter Philip Schofield and actor Benedict Cumberbatch and popularised by Dr Michael Mosley in his book The Fast Diet, the 5:2 approach allows you to eat as normal for five days of the week but fast on the other two, limiting your calorific intake to around 800 a day.

Recently, Dr Mosley has also promoted ‘The Fast 800’, a new 12-week schedule that involves cutting your calories to a limit of 800 per day for the first two-weeks before reverting to the 5:2 plan. Additional benefits are said to include improvements in your blood sugar levels and your blood pressure.

Read more: Creator of 5:2 diet shares two easy exercises to aid weight loss

3. The 12:12 method

Fasting for 12 hours a day is a good place to start if you’re thinking of taking the plunge, not least because you’ll be asleep for most of the time you’ll be refraining from eating. Try having your last thing to eat before 7pm, and no less than two hours before you go to bed, and then eat again once you’re awake, after 7am.

4. Alternate Day Fasting (ADF)

Two ways to approach this method of fasting every other day. Either avoid solid foods entirely on your fasting day or allow yourself around 500 calories on those days, before returning to your normal eating regime on non-fasting days. There’s strong evidence to suggest it is effective too. In one study published in Nutrition Journal in 2013, 32 people who took part in an ADF trial lost an average of 5.2 kilograms (kg), or just over 11 pounds (lb), over a 12-week period.

5. The Warrior Diet

When a fasting regime has a name like ‘Warrior Diet’ you can probably guess that it’s a little on the extreme side. This one involves a marathon 20-hour fast, with an eating window of just four hours and participants usually eat just one large meal at night. Proponents maintain that humans are naturally nocturnal when it comes to eating and that taking food during the night allows the body to maximise the nutrients it needs alongside our circadian rhythm.