Back in 2012 I made a science documentary called Eat, Fast And Live Longer which explored the science behind approaches to extending healthy life and holding back the hands of time. I concluded that the only proven way to do this was by calorie restricting.


Now, eight years later, there’s stronger proof of the benefits from calorie restriction or intermittent fasting (where you reduce your calories for two days a week).

The first evidence came from researchers at Cornell University in the 1930s. A team led by Dr Clive McCay decided to put a group of mice on a low-calorie diet. They were amazed to discover that mice who were fed 30 per cent fewer calories than normal, lived 40 per cent longer.

The longer-lived mice were also less prone to normal age-related illnesses, such as cancer and heart disease.

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Subsequent studies have shown the same is true for almost every other animal species that has been put on a calorie-restricted diet – they not only live longer but are far more healthy.

So what about humans? In a recent study, CALERIE (Comprehensive Assessment of the Long-Term Effects of Reducing Intake of Energy), researchers tested the effects of long-term calorie restriction on non-obese people.

In the study, 218 healthy people of a normal weight were randomly assigned to either cutting daily calorie intake by 15 per cent for two years, or continuing as normal.

Those in the calorie restriction group, not surprisingly, lost weight (an average of nine kilograms) but also saw big improvements in a range of risk factors, including cholesterol, blood pressure and C-reactive protein (a measure of inflammation). They also reported improvements in sleep, mood, sex drive and quality of life.

© Jason Raish
© Jason Raish

As one of the lead researchers, Leanne Redman, associate professor of Clinical Sciences at Pennington Biomedical Research, puts it, “We found that even people who are already healthy and lean may benefit from a calorie restriction regimen.”

How does it work? Well, another recent finding is that calorie restriction suppresses the normal age-related increase in inflammation, something widely recognised as a major driver of dementia, heart disease and cancer.

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Personally, I find the idea of long-term calorie restriction a bit too challenging, which is why I decided to put myself on the 5:2 diet, a now popular form of intermittent fasting.

It dramatically improved my health and I was delighted to read a recent paper in the New England Journal Of Medicine which looked at all the available research and concluded that the benefits of intermittent fasting are widespread.

The paper said that intermittent fasting not only improves blood sugar regulation and blood pressure, but increases resistance to stress and suppresses inflammation.


All good reasons to cut back a little.


Dr Michael Mosley is former medical doctor, health writer and BBC presenter. He’s best known as presenter of Trust Me I’m a Doctor on BBC Two but has also written a number of bestsellers about personal health and medicine, including The Fast Diet, Fast Asleep and Fast Exercise.