Is is true the 5:2 diet now allows 800 calories on a fast day?


In recent months it has been reported that Dr Michael Mosley, author of the original The Fast Diet book, has ‘relaxed the rules of 5:2’ by increasing the fast day calorie allowance to 800 calories for men and women alike – that’s an extra 200 calories for men and a whopping 300 calories for women.

Fasting on 800 calories is really nothing new to the world of intermittent fasting, as ADF (alternate day fasting) has been using this figure for years and indeed some following a 4:3 fasting regime (3 fasting days a week) allow themselves this slightly higher calorie limit too.

While we agree that 800 calories may be easier for those who struggle with the original 5:2 diet calorie restrictions and that any calorie deficit can only be a good thing when trying to lose weight, many reports about this so-called change to the plan are incomplete and slightly misleading.

Dr Mosley is reported to have said:

“You don’t need to stick to 600 calories. Cutting down to 800 calories a day seems to be almost as effective and for some people much more ‘doable’.”

“It’s low calorie, without being superlow-calorie. And if you want to have lunch, you can slip those extra 200 calories in there.”

However, what often missed out in these reports is that Dr Mosley also says that if having 800 calories on your fast days, you should follow a low-carb/Mediterranean style diet for the other 5 days for it to be as effective in terms of weight loss. While Mediterranean style eating may be normal for some, for others it will feel more like a full time diet, with daily restrictions and less freedom than allowed by the original style 5:2. Not that normal 5:2 should be used an an excuse to binge or make poor food choices on every non-fast day, but certainly its flexibility and the part-time nature of the plan is key to what has made it so sustainable in the long term. We all know long term compliance is a big issue when it comes to a diet (or, ‘way of eating’ as we prefer to call 5:2, as ‘diet’ can imply a fad or short term fix) and the best plan for anyone is one that they can stick to.

Certainly it’s good advice to reduce the amount of processed and sugary foods we eat, but doing so can involve more willpower and may make this ‘new style 5:2’ on 800 calories somewhat more difficult to stick to than the original form. Another point to note is that with a lesser calorie deficit, weight loss results may be slower (if not combined with low-carb/Med eating on the other days) and this can be disheartening for a new starter.

Keep it simple for starters, that really is the joy of 5:2.

Our advice? Stick to pure 5:2 and before long you’re likely to find yourself making healthier choices on the other 5 days anyway. When you reach your goal weight perhaps then could be a time to consider switching to 800 calories on your fast days for maintenance purposes.

If you’re already a low-carber however and looking to shake things up a bit, perhaps fasting twice a week on 800 calories would be a helpful new addition to your weight loss arsenal!


Have you tried the ‘new style 5:2 diet’? Share your results with us in the comments!

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