Diets explained: The 5:2 fasting diet

Last year journalist Michael Mosley produced a documentary called Eat, Fast and Live Longer. It sparked the latest dieting craze – the 5:2 diet, also known as the fasting diet or intermittent fasting.

The fasting diet is not actually about losing weight – that’s just a happy side effect. Mosley looked into this diet because it is supposed to drastically reduce all of the major risk factors associated with ageing. In theory, eating in this way should significantly reduce your risk of heart attack, diabetes, dementia and cancer.

The diet
The rules are thus: five days per week you can eat what you like. You can literally eat as much of any kind of food you can think of as you desire. High fat, high sugar – it doesn’t matter. Of course, eating healthily is always preferable, but to get the benefits of this diet it isn’t necessary.

Then, on the other two days, you can only consume a restricted number of calories per day – 500 for women and 600 for men. You could blow those calories on half a donut, but eating lean, high protein and high fibre foods will keep you fuller for longer and help to keep your energy levels up.

The science
So how does it work? In western society we rarely go without food for more than a few hours. This constant snacking keeps blood sugar levels consistently high. It means that our body rarely eats through all the sugar and moves on to burning fat. This allows the fat to accumulate over time, causing high cholesterol, extra stomach fat and an increased risk of heart disease and diabetes.

It also keeps your IGF-1 levels high. IGF-1 stands for Insulin-like Growth Factor 1. It is a growth hormone which has been strongly linked to hormone-influenced cancers, such as breast and prostate cancer.

When you have too much IGF-1 your body keeps producing new cells instead of repairing the cells you’ve already got. Every time a cell splits into two new cells, there is a chance it will mutate, which is how cancer cells start. The more new cells you produce, the higher your chance of cancer, which is why having high IGF-1 levels is a problem – it causes your body to produce new cells when it could be repairing the old, cancer-free ones.


Click NEXT to find out if this diet works

The results
During the documentary, Michael Mosley tried a number of different fasting diets. He found the 5:2 ratio the easiest to fit into his everyday life.

Before he started the 5:2 diet, he had some tests done, so he could see if the diet was actually effective.

BMI: 26.4
Body fat: 28 per cent
Waist size: 91cm

Fasting glucose: 7.3 – puts his diabetes risk as high
Triglycerides: 1.4 – within healthy parameters
HDL (good) cholesterol: 1.8 – within healthy parameters
LDL (bad) cholesterol: 5.5 – quite a high level
IGF-1: 28.6 – at the top end of the healthy range

BMI: 24
Body fat: 21 per cent
Waist size: 83cm

Fasting glucose: 5.0 – within healthy parameters
Triglycerides: 0.6 – within healthy parameters
HDL (good) cholesterol: 2.1 – within healthy parameters
LDL (bad) cholesterol: 3.6 – still slightly high
IGF-1: 15.9 – well within healthy parameters

After just six weeks on the 5:2 diet, Michael Mosley’s BMI dropped to a healthy level, his body fat percentage dropped seven per cent, he lost 8 cm off his waist, his diabetes risk dropped back to a healthy range and his cholesterol went down to a healthy level. His cancer risk was also significantly reduced.

Is this the right diet for you?
Unless you have type 1 diabetes, fasting is not considered to be dangerous by many health professionals. The results here are from just one person, which is not conclusive evidence, however there have been a number of other studies which show the benefits of this diet. Before making any dietary changes you should always talk to your GP or health professional.

You can watch the documentary on the Documentary Heaven website

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