THE FAST DIET: Get Thin Quick By Starving Yourself Two Days A Week

Fast DietPhoto courtesy of Atria BooksA typical FastDiet meal.

The FastDiet, also known as the 5:2 diet, is based on something called intermittent fasting.

This involves eating normally for five days a week and “fasting” for two. On those two fasting days, you eat about a quarter of your typical calorie intake — 500 calories for women and 600 calories for men. The rest of the time you can eat whatever you want.

The book, released last year in the U.S., was written by Dr. Michael Mosley and Mimi Spencer, both of the U.K. They claim this diet will make you lose weight faster than other standard diets. Mosley claims to have lost 20 pounds within a few weeks of starting the diet.

Although the extreme eating regime has been met with criticism in the health community, Mosley says the evidence to support intermittent fasting is there. The entire first chapter is devoted to the “science of fasting.” And, some fitness experts have come out in favour of the diet. A 2007 review also found that alternate-day fasting may moderate disease-risk.

Here we break down how and why the 5:2 diet works, according to its authors.

The 5:2 diet, based on intermittent fasting, is different from calorie restriction or starving.

Dr. Michael Mosley and Mimi Spencer are both on the FastDiet.

Intermittent fasting is not the same as prolonged calorie restriction, or starving. That would be when our body doesn't take in enough nutrients to maintain a normal, healthy lifestyle.

Intermittent fasting involves 'eating fewer calories, but only some of the time,' Mosley writes.

Mosley admits that prolonged fasting is not sustainable and will ultimately result in muscle loss.

With the FastDiet, you never go for longer than 24 hours without eating.

Source: The FastDiet

Ok, so where's the science?

Intermittent fasting improves learning and memory by stimulating new brain cells in the region of the brain responsible for memory.

In a study with mice, neuroscientist Mark Mattson found that intermittent fasting increases levels of a protein called brain-derived neurotrophic factor, or BDNF.

This, in turn, stimulates new brain cells in the hippocampus, the region of the brain that is responsible for memory. (Shrinking of the hippocampus has been linked to dementia and Alzheimer's disease).

In the lab, Mattson fed one group of mice a diet of junk food, while a different group of mice ate a low fat diet and fasted for part of the week. The mice fed junk food became fat and had more problems navigating the maze to find food. The fasting mice had more BDNF in their brains.

Source: The FastDiet

Intermittent fasting improves your mood.

Earlier we mentioned a protein called brain-derived neurotrophic factor, or BDNF, that helps improve memory. It turns out the same protein has been shown to suppress anxiety and elevate mood.

Mattson showed this to be true in a study of rats. He injected BDNF into their brains and it had the same effect as a regular antidepressant.

Again, this test hasn't been performed on humans.

Source: The FastDiet

There are downsides to fasting, too.

So far you've learned how fasting can help us live longer, look younger, and ward off memory loss. But not everyone buys into this diet.

'Despite its increasing popularity, there is a great deal of uncertainty about IF with significant gaps in the evidence,' Britain's health agency, the National Health Service, wrote on its website after the book was published in January ('The FastDiet' hit U.S. bookshelves in mid-March).

Lisa Moskovitz, a Manhattan-based registered dietitian agrees: 'There is limited evidence that shows a few days of calorie restriction will have any better results than following a moderately restricted calorie diet on all days of the week,' she told us in an email.

1. Get yourself to a doctor.

We do not recommend starting this diet without the supervision of doctor and before getting the necessary tests.

Moskovitz also shares a warning: 'While the diet may not be dangerous for everyone, I would not recommend this plan for anyone with diabetes as it can affect blood sugar medications. I would also not recommend this type of eating for intense exercisers either, especially on fasting days as it can be hard to sustain activity.'

3. Decide what days you are going to fast.

Everyone on the diet will eat normally five days out of the week and limit calories for two of those days. But you can decide how to split up those calories.

Mosley decided to split his 600 calories between breakfast and dinner. Spencer chose to eat two meals with a few snacks in between.

There is some evidence, according to the authors, that going for a longer period of time without eating produces better results, meaning Michael's strategy could be more effective.

Source: The FastDiet

Here is an example of a 500-calorie meal: Breakfast includes cottage cheese, a sliced pear, and a fresh fig. Dinner is salmon and tuna sashimi with soy sauce, wasabi, pickled ginger, and a tangerine.

Source: The FastDiet

Here is an example of a 600-calorie meal: Breakfast is boiled eggs, asparagus spears, whole grain toast, and two plums. Dinner is Thai steak salad.

Source: The FastDiet

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