The diet that has you cutting 75% of your food intake twice a week.

Brace yourselves. A new diet is going viral, because that’s what diets do now. Sugar-free, anyone?

Tellingly, it’s called “The Fast Diet” and it comes from a new book written by Dr Michael Mosley and Mimi Spencer. Dr Mosley is a medical journalist and Mimi Spencer is a food and fashion writer.

Both are from the UK, where their book has been a number-one bestseller for weeks.

The Fast Diet is also known as the 5:2 diet. It involves five days of normal eating, and two days of fasting. According to the authors, the two (non-consecutive) days of fasting per week will result in the metabolism working harder on the days you DON’T fast. This is intended to result in weight loss and general better health all round.

This from the Fast Diet website:

That’s five days of normal eating, with little thought to calorie control and a slice of pie for pudding if that’s what you want. Then, on the other two (non-consecutive) days, you just eat a quarter of your recommended daily calorie quota. That works out at 500 calories for women and 600 for men.

To give you a bit of an idea about how far those 500 calories could stretch: one medium banana has about 100 calories. One orange also has about 100. There are about 250 calories alone in a cup of plain cooked pasta. Add a bit of sauce and cheese and you’ve probably reached your limit for the day.

Normal daily intake for a woman is 2000 calories. So you’re basically cutting your recommended food intake by 75 per cent. Feeling hungry yet?

The authors reckon that The Fast Diet is easier to follow than other diets because you’re only actually dieting for two days per week and there is “always something new and tasty on the near horizon”.

“In short, it’s easy to comply with a regime that only asks you to restrict your calorie intake occasionally,” they claim.

This Fast Diet started with Dr Mosley, who decided to try fasting last year because of his high blood sugar levels, high cholesterol and visceral fat in his gut.

Although never obese, his BMI and body fat percentage were higher than what was recommended for men. He also had a history of diabetes in the family and, looking prediabetic, wanted to change something in his diet.

He decided to film his intermittent fasting and turned it into a BBC documentary called “East, Fast and Live Longer”. In the documentary, he also interviewed scientists about the potential results of fasting.

This from the New York Times:

The prominent benefits, he discovered, were weight loss, a lower risk of cancer and heart disease, and increased energy. “The body goes into a repair-and-recover mode when it no longer has the work of storing the food being consumed,” he said.

Though Dr. Mosley quickly gave up on the most extreme forms of fasting (he ate little more than one cup of low-calorie soup every 24 hours for four consecutive days in his first trial), he finally settled on the 5:2 ratio as a more sustainable, less painful option that could realistically be followed without annihilating his social life or work.

The documentary then led to the book, which has taken off worldwide.

Both Dr Mosley and Mimi Spencer say they have lost about 9kg by following the diet and similar testimonials are now flooding in via social media and online. Hugh Fearnley-Whittingstall, a food writer at The Guardian in the UK, is one of those who tried the diet, despite not being “any kind of dieter”. Here’s what he had to say about it:

…As I write, I am on my sixth day of fasting since I started on New Year’s Day. I feel lean and sharp, and although I’ve had some pangs of hunger through the day, a few cups of black tea and rooibos have kept them at bay. I’m just an hour away from my light supper of bream fillet baked with chilli, ginger and soy, a spoonful of rice and a large leafy salad, and I’m certainly looking forward to it.So I believe in this fasting thing, I really do. With my strictly non-snacking version, I’ve lost eight pounds already, and I find the whole thing rather exhilarating. I feel I might just be part of a health revolution.

It’s worth noting that there are certain groups for whom the diet is NOT advised. Those who are pregnant, or suffering from an eating disorder, or Type 1 diabetics should not fast. It’s also recommended that children and those who are already extremely lean never fast.

And not everyone is supporting the move towards fasting. In recognition of the diet’s newfound popular, Britain’s publicly funded medical program, The National Health Service, have put this statement on their website: “Due to the very real uncertainties about the 5:2, especially as little is known about whether it could be harmful to health in the long-term, most health professionals would recommend you stick to the tried and trusted methods for weight loss and disease prevention: eating a healthy balanced diet with at least five portions of fruit and vegetables a day,taking regular exercise, quitting smoking if you smoke, drinking alcohol in moderation.”

Another Guardian article has slammed the diet as a “recipe for unhappiness”, saying that advocating abstinence is like advocating self-abuse. This from scientist and writer Sian Lawson:

I am a well-educated scientist, but I am also someone who has struggled with anorexia, albeit many years ago. This is why I am shocked to see mainstream broadsheets publishing pieces that I personally see as essentially encouraging self-abuse.

After all, it is unlikely that the routine January attack on our self-esteem would be so well received if it proposed that women shouldn’t worry themselves about business matters, as a little work-stress can always be relieved by cutting your arms.

But somehow, the idea that normal, healthy eating is a vice to be eliminated is unleashed on to the public, as if there were no potential danger to raising the social acceptability of this viewpoint.

Do you think the Fast Diet sounds ridiculous or reasonable? 

*Please note that Mamamia does not advocate readers trying The Fast Diet. In fact we don’t recommend any diet other than those that have been advised for medical reasons.