IF EVERY YEAR has a new popular post-Christmas diet, 2013′s is the Fast Diet, which claims to boost not only weight loss, but overall health.

With Twitter ablaze with #fastdiet and #fastdietirl hashtags, TheJournal.ie spoke to a dietician and a fan of the diet to find out more.

The Fast Diet

The man responsible for the Fast Diet is Dr Michael Mosley, who wrote the bestselling book with fashion and food writer Mimi Spencer. The book followed the 2012 Horizon documentary in which Mosley explored the world of intermittent fasting.

According to the Fast Diet book, intermittent fasting is something that humans have done for centuries, whether for social, religious or other reasons (such as the fact that the hunter-gatherer lifestyle didn’t lend itself to eating very regularly).

In the book, Dr Mosley, describes how tests on mice showed that fasting could have a beneficial effect on brain function, which was a further reason for him to explore the diet.

While the average person would be advised to eat up to 2,000 calories a day for women or 2,200 for men, the Fast Diet – also known under the less-catchy moniker of the 5:2 Diet – dictates that women eat 500 and men eat 600 calories on two non-consecutive days a week. The aim is to then eat ‘well’ for the remaining five days – no gorging on fast food – and the weight will, they say, drop off. But is this healthy?

The Dietician

For dietician Sarah Keogh of the Irish Nutrition and Dietetic Institute, the Fast Diet is “very popular because it’s the latest diet – every few years a new one comes along. Like a lot, it will be around and then run its course”.

Keogh noted that fasting was also popular around 15 – 16 years ago:

The new idea is that you don’t completely fast; that you would still eat 50o or 600 calories. It’s more that you’re resting on those days than actually fasting. It can be quite helpful in people losing weight, but the concern I would have for a lot of people is to make up the nutrition they need for the whole week can actually be quite difficult. If you cut food for two days you’ve lost more than calories.

Keogh pointed out that people fasting might have less than the recommended three servings of calcium a day, which is concerning given that 50 per cent of women and 20 per cent of men get osteoporosis in Ireland.

She also expressed concern that people wouldn’t get all of the minerals they need on the diet. “With iron – if you’re really restricting your food on a day that can be a problem,” she said. “You do still need to look at your diet the days you’re not restricting.”

Keogh believes some people have have the wrong idea bout the diet, thinking the non-fast days mean stocking up on calories. “It will run its course,” she said.

When they talk about the health gains I would love to see more study on it. There have always been arguments that a little bit of fasting is good for you. People would often talk about the cleansing effect of nothing going into the bowel.

I agree the body does adapt to fasting but I’m not convinced the body does very well out of it.

The appeal of the diet? “I think what appeals to a lot of people is that you only have to work at it two days week,” said Keogh.

I do think it’s a fad but it’s an interesting one.

The dieter

One fan of the Fast Diet who has become a champion of it on Twitter is food blogger Paula Ryan of Paula’s Kitchen Table. She read a magazine feature on the diet, which in turn led her to the Horizon documentary.

The diet caught Ryan’s eye because of the touted health benefits. “It’s really interesting – it kind of made sense. [Dr Mosley's] wife was a GP and she was really positive about it.”

But there could be downsides. “It could be a diet that could be abused. I eat well anyway and I run,” she pointed out.

“If you’ve had problems in the past with eating disorders, this is not for you,” cautions Ryan. “It’s like every diet – you have to take a healthy approach to it as well.” That means no frozen meals, and an emphasis on real wholesome food.

I prefer to do it and do the homecooked stuff, and do it in a healthy way.

I’m sticking to a veggie diet, using beans as protein just to fill me up me a little more.

On her normal days she just eats when she normally would eat. Having lost a number of pounds on the diet, Ryan says she will continue with two fast days until she reaches her goal weight, and then will probably do one fast day a week.

The diet has shown her “we are eating such huge portions”, she said, adding: “It’s not a diet – you’re changing your lifestyle.”

Sometimes if you’re on a diet all you can think about is food. But if I bake a cake on the day of the fast, and if I fancy a slice of cake it’s great to know I can have it the following day. You don’t feel deprived.

The Fast Diet is the latest in a long line of popular diets:

Cabbage soup diet

Fancy eating cabbage soup all day? Us neither. Interestingly, this diet allows people to eat nothing but cabbage soup and certain specified fruit, vegetables, skim milk and meat for seven days. It’s not as bad as just eating cabbage soup, but it takes calorie restriction to the extreme.

Maple syrup diet

Once allegedly beloved of Beyoncé, this is a frankly bizarre diet that involves just drinking pints of a concoction of maple syrup, lemon juice and cayenne pepper mixed with water. It’s no surprise to find out that today it’s not the hip diet it was very briefly in 2007. Phew.

The Atkins Diet

Eating nothing but bacon all day long? That’s what many people think when you mention the Atkins Diet, which was hugely popular in the early 2000s. Devotees of this low-carbohydrate diet loved that it meant eating lots of meaty protein, but the side effects – which allegedly include bad breath and lack of energy – led to it falling out of favour within a few years.

The South Beach Diet

Another low-carb diet, this one focused on a low-sugar approach and aims to stabilise blood-sugar levels. Probably not as fun as spending time on an actual beach.

Baby Food diet

A diet based on eating baby food was never going to be popular for very long, now was it?

Read: Forget the New Year’s diet? Being slightly ‘overweight’ extends your life>

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