You might be wondering how a Prime Minister with a demanding schedule looks after his health, and Rishi Sunak has revealed he does intermittent fasting as part a “balanced lifestyle”.

Describing it as an “important discipline”, Sunak typically doesn’t eat on Monday, which he says helps him combat his “weakness for sugary things” – apparently he loves Coca-Cola.

He told BBC News: “I tend to try and do some fasting at the beginning of every week as part of a general balanced lifestyle but everyone will do this differently.”

Asked about how he fasts for a day despite the demands of his office, Sunak said: “That’s an important discipline for me but it means that I can then indulge myself in all the sugary treats that I like for the rest of the week, which I tend to enjoy. That’s where I balance it with my job and everything else.”

Friends of Sunak told The Sunday Times that he does not eat anything for 36 hours at the start of each week, from 5pm on Sunday until 5am on Tuesday. Downing Street insiders disputed the timeline but confirmed that he typically fasts on Mondays.

Any fasting diet like this should be approached with caution though, and many health professionals are dubious about the touted benefits.

What is intermittent fasting?

Instead of just focusing on what you eat, intermittent fasting encourages people to think about when you eat. The idea is, you only eat during a specific time period, the theory being that this gives your body a break from digesting food.

Some people claim that intermittent fasting mimics the traditional eating patterns of our ancestors, who would have to fast because of lack of food availability until they had hunted or foraged for it.

It’s recommended to replenish the body with enough of the right nutrients whenever the fast is over.

What are the different types?

People are advised to speak to their doctor before trying intermittent fasting, because some fasts could be more taxing on the body than others.

There is the 16/8 plan, where people only eat during an eight-hour window but fast for remaining 16 hours (which includes nighttime). For example, eating between 10am to 6pm, and then drink water, milk, tea or coffee for the remaining time. Some opt for a longer eating window of 10 hours.

The 5:2 diet is also based on the principles of intermittent fasting – only consuming 500 to 600 calories for two days each week, and then eating a normal, balanced diet on the other days.

Alternate-day fasting, is considered one of the more extreme approaches, and may not be safe for everyone.

A weekly one day fast, similar to Sunak’s method, is known as eat-stop-eat diet.

What are the pros and cons?

There are limited studies into intermittent fasting and it’s supposed benefits, so health professionals simply don’t know enough yet.

A 2023 study by the University of Illinois Chicago found intermittent fasting is ‘as effective as counting calories’ – when limiting food to a eight hour window. The study found that weight loss wasn’t dramatic, but that people were more able to stick to the plan consistently – compared to calorie counting.

Research published by the University of Glasgow, Teeside University and the Independent Public Health Consultant in 2018 suggested intermittent ‘energy restriction’ may be an effective strategy for the treatment of overweight and obese adults – and more effective than not doing anything.

A previous study published in 2013 examined the results of fasting for 24 hours. The researchers studied 16 people who fasted (but could eat 25% of their daily caloire allowance on fast days) compared to 16 who didn’t over three months. The fasting group did show reduced weight, body fat and improved markers for cardiovascular disease.

Fans of the practice claim they feel various benefits, from a boost in memory and cognitive function, to improve blood pressure, better blood sugar control and weight management.

But negative side effects have been reported too, including insomnia, irritability, headaches, lightheadedness, digestive issues, poor concentration and nausea. It’ll come as no surprise that hunger is a side effect too.

The idea is, when you go hours without eating, your body eventually runs out of stored sugar to use, and it begins to burn fat to produce energy instead. But going for very long periods, over 24 hours, is more controversial – it might cause the body to think it’s in starvation mode.

Plus, findings by the University of Toronto, published in Eating Behaviors in 2022, linked intermittent fasting with disordered eating and potentially dangerous, compulsive behaviors in young people.

Intermittent fasting is not recommended for people who are pregnant, have type 1 diabetes or have a history of disordered eating. Anyone with pre-existing medical conditions should consult their GP before making any major changes to their diet.