5:2 Diet or Intermittent Fasting

The 5:2 diet or intermittent fasting: what is it and how does it work?

As I’ve written before, I’m not a big fan of “diets”; in the long run they don’t work. As soon as you start eating “normally” again, the weight just piles straight back on. However, finding a way of eating that you can incorporate into your life for the long term is an interesting proposition and “intermittent fasting” fits the bill.

Fasting is an interesting concept which is popular within various religions as a way of cleansing the body. The prophet Mohammed apparently advocated fasting on Tuesdays and Thursdays. There is little human research but plenty of animal studies to suggest that fasting or restricting calories leads to longer life.

The basic premise is that on 2 days each week (for example Tuesday and Thursday) you consume 500 calories or less (as a woman, 600 if you are a man). On the other 5 days you eat pretty much what you want, although research has shown that as weight loss occurs you are less inclined to overeat.

The diet was reviewed (and tried) by Dr Michael Mosley, the results of which were the subject of a TV documentary for Horizon on BBC2. Dr Mosley is a medical doctor, journalist and television presenter who wanted to lose weight, reduce blood glucose levels (bordering diabetic) and lower cholesterol (at levels requiring medication).

He met with various scientists and one,  Dr Krista Varady of the University of Illinois at Chicago,  told him about a diet that she has been testing on human volunteers. It’s called Alternate Day Fasting (ADF) and is very simple. One day you eat whatever you want. The next day, you fast.

Dr Varady has finished a trial, to be published next month, in which she took two groups of volunteers doing ADF for 10 weeks. One group was put on a low-fat diet on their feed days, while the other was encouraged to eat lasagne, pizza — a typical American high-fat diet. As Dr Varady explained, the results were unexpected.

“When they signed up for the study, the people randomised into the high-fat group weren’t happy because they assumed that they wouldn’t lose as much weight as those randomised to the low-fat diet. But they did. People on the high-fat diet were losing as much and sometimes more weight, week after week.”

You can read the results on the University of Illinois website.

Dr Mosley decided that ADF was too extreme for him to continue for any length of time so he adjusted the diet to 2 fast days out of 5. He followed the diet for 6 weeks before having a second medical. The results were impressive. He had lost well over a stone, down to less than 12st. His blood glucose, which had been borderline diabetic, was normal and his cholesterol levels, previously high enough to necessitate medication, were also down in the healthy range.

Intermittent fasting is not for everyone, as with any diet you should consult your GP, especially if you are diabetic or on medication. However, the results seem to be impressive and it is a way of eating that you can incorporate for the long term.

Here are the main bullet points of the diet:

• With the 5:2 diet, you can eat whatever you like five days a week — so-called feeding days. On the two “fasting days” you eat 500 calories if you are a woman, or 600 calories if you are a man.

• It doesn’t matter which days are spent “feeding” and which “fasting”, as long as the fasting days are non-consecutive and you stick to the 5:2 ratio.

• On fasting days you can consume your calories in one go, or spread them through the day — there is no medical research into whether filling up at breakfast or snacking throughout the day is more effective for weight loss.

• A typical fasting-day breakfast of 300 calories might consist of two scrambled eggs with ham (good sources of protein), plenty of water, green tea or black coffee. For a typical 300-calorie lunch or dinner, try grilled fish or meat with vegetables.

• On feeding days you can eat whatever you like. Most dieters, rather than feeling a need to gorge, found that they were happy to consume around 2,000 calories — the recommended daily intake for women (2,600 for men) — and did not crave high-fat foods.

• Contrary to popular opinion, fasting can be a healthy way to lose weight. It can reduce levels of IGF-1 (insulin-like growth factor 1, which leads to accelerated ageing), switches on DNA repair genes and reduces blood pressure, cholesterol and glucose levels.

• According to current medical opinion, the benefits of fasting are unproven. As a diet, it is not recommended for pregnant women or diabetics taking medication. Anyone considering a diet that involves fasting is advised to consult their GP first, and to do it under medical supervision.

Finding recipes for a fasting day can be difficult but Xanthe Clay (food writer for the Telegraph) has come up with some fabulous recipes, all around 250 calories (find them here). They are truly delicious and you might want to try them without the fast!


My name is Caroline Sutton and I'm a wife and mother of 3 children, passionate about food, keeping me and my family healthy, gorgeous interiors and shopping! I have a degree in Biochemistry and Pharmacology and continue to be interested in the science behind diet and drugs. I also have a Diploma and City and Guilds in Interior Design and for the last 17 years have run a property company which develops, redevelops and manages rental properties: Sunlight Properties Ltd.

Posted in Adult Health, Health, Weight Loss

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