Fasting has become the latest dieting fad, and the superstar of the moment is Aidan Turner of BBC series Poldark. But is it any good?

Media in the UK have gone berserk over images of Turner’s naked torso emerging from the surf of Cornwall and the extraordinary lengths he goes to in maintaining his magnificence.

Turner, who eats nothing until 7pm, has essentially adopted a Ramadan approach to eating all year around. Except Muslims are allowed breakfast before dawn.

He also works out twice a day. This is important to keep in mind. For the stars of stage and screen, keeping the body in money-making shape is part of the job. Cross-training and avoiding doughnuts is what they’re doing while we’re photocopying and struggling with spreadsheets. And they have team support to help them maintain the discipline of fasting for long periods of time.

Plenty of other celebrities swear by fasting.

Ben Affleck copped a cruel serve in New Yorker magazine recently, mainly because his belly had blown out to truckdriver proportions. Ben’s solution? Intermittent fasting, apparently: going for most of the day – or whole days – without food, and lo the weight drops off.

Beyonce relies on the same strategy when her fab curves get ahead of themselves. Hugh Jackman? No food for 16 hours a day – known as the 16:8 diet – keeps him from a ruinous dad bod.

Then there’s the alternate day fasting: eat normally one day, live on water or no more than 500 calories the next, repeat forever. There’s the 5:2 – five days eat, two days don’t.

And there’s the Warrior Diet: nothing until dark, and just one big meal.

Hugh Jackman, Beyonce Knowles-Carter and Ben Affleck all swear by intermittent fasting to stay trim. Photos: Getty

So should you try fasting?

The short answer is: according to a 2015 review of 12 clinical studies, intermittent fasting is as good as any other form of dieting, for the time you stick to it. As study authors noted: “Intermittent fasting thus represents a valid – albeit apparently not superior – option to continuous energy restriction for weight loss.”

Where traditional diets involve a reduced caloric intake spread out even over the days, fasting involves reducing your calories to nothing for hours or days at a time. Stick to either method and you lose weight. Fasting just does it faster, but is more difficult to sustain.

As the American Heart Association said in a 2017 statement: “There is evidence that both alternate-day fasting and periodic fasting may be effective for weight loss, although there are no data that indicate whether the weight loss can be sustained long term.”

And a 2017 study found that intermittent fasting was particularly helpful to obese men, who experienced a greater weight and fat loss than following other methods. The combination of fasting and eating seemed to combat a drop on metabolism “and, in turn, improve weight-loss efficiency”.

But forget those claims that fasting will make you enjoy long-lasting health benefits. Yes, studies have shown that fruit flies and mice will live up to a third longer when their calorie intake is reduced by almost half. Not so for primates. A 25-year study of rhesus monkeys found no increase in lifespan linked to calorie reduction.

The evidence simply isn’t there that you’ll live longer and better, says Professor Lynn Riddell from the Institute for Physical Activity and Nutrition at Deakin University.

However, she said some people with type-2 diabetes have benefited from intermittent fasting, to the extent they have been able to go off their medication. “But that should occur only under medical supervision.”

Professor Riddell said that while intermittent fasting has merit, for some people “you need to be careful with fasting”.

“When we’re hungry we make poor food choices,” she said.

“Some people get too hungry through the course of the fast and go for instant hunger fixes. So they only fail but with bad choices.”

Professor Riddell added that fasting should be avoided by people who have had eating disorders. “It can be a trigger. It’s known to have happened.”

Other people who should avoid fasting include those who take food-related medication, people with food time insulation requirements, young people undergoing growth phases, and pregnant or breastfeeding women.