Was I wrong all along about intermittent fasting?

As a new study suggests it can raise your risk of a fatal heart attack...

IWAS shocked and surprised to see the headlines this week suggesting that intermittent fasting — specifically a type known as time-restricted eating (TRE) — could be bad for your heart, increasing your risk of a fatal heart attack.

after the news broke, my phone ran hot with calls asking me to comment — as, like many others, I have for years been incorporating different elements of intermittent fasting into my daily routine, to help manage my weight and keep my blood sugar levels down. In fact, intermittent fasting is a central part of my bestselling Fast 800 diet.

Over the past decade I’ve talked to plenty of experts, read lots of research and taken part in studies which have all shown how beneficial intermittent fasting can be. But will this new study change my mind?

There are lots of different forms of intermittent fasting, including the 5:2 diet (where you cut calories two days a week) to time-restricted eating (TRE), where you simply reduce the hours within which you eat.

Essentially, it’s a way of giving your body a break from digesting food, to help trigger a process called autophagy, a form of cellular ‘spring cleaning’, where old cells are broken down and recycled.

A2009 review of the best research, published in the New England Journal of Medicine, concluded that ‘intermittent fasting has broadspectrum benefits for many health conditions, such as obesity, diabetes mellitus [type 2 diabetes], cardiovascular disease, cancers and neurologic disorders [such as dementia]’.

so I was very puzzled by this new research which suggests that following a 16:8 pattern of timerestricted eating (fasting for 16 hours and eating during an eighthour window) is linked to a 91 per cent higher risk of death from cardiovascular disease.

Could I and so many others have got things spectacularly wrong?

I’ve read the study abstract — which is all that is currently available and is essentially the summary — and I’m convinced there is nothing to worry about.

The so-far unpublished study, by researchers at shanghai Jiao Tong University school of Medicine, looked at data from the

U.s. National Health and Nutrition Examination surveys, collected between 2003 and 2018.

In these surveys, americans were asked about their eating habits.

what the researchers in China did was pick out those who had ticked a box saying that on two separate occasions they’d restricted their food consumption to an eight-hour window or less.

They then cross-referenced these people to the U.s. National Death Index database to see what happened to them.

It turned out that those who’d ticked that box had almost twice the risk of dying from heart disease than people who had not ticked those boxes. There are lots of problems with trying to make sense of this study, not least because we don’t know how old the participants were, how healthy they were, whether their recall was accurate and, importantly, whether those two days were representative of what they did the rest of the week.

as Kevin McConway, an emeritus professor of applied statistics at the Open University, pointed out: ‘we don’t know whether their eating times over those two 24-hour periods was typical of the times they usually ate. so to relate those patterns to a deliberate long-term time-restricted eating intervention seems to be going far beyond the data’. sir David spiegelhalter, an emeritus professor of statistics at the University of Cambridge, agreed, adding somewhat scathingly: ‘This abstract should not have been graced with a press release.’

OTHER experts pointed out that the people who reported only eating in an eight-hour window might have done so because they had previous heart problems or had eaten that way because they were doing shift work, which is itself linked to an increased risk of heart disease and type 2 diabetes.

Finally, we have no idea what these people were consuming. was it a healthy Mediterranean diet, or processed junk food?

so no, my belief in the benefits of intermittent fasting has not been shaken by this abstract.

If you’re happy on your TRE regimen, the latest research suggests it’s better to eat more of your calories earlier, avoiding a large evening meal.

a study published in the journal Nature Communications involving 100,000 adults found eating breakfast before 8am and stopping eating 12-13 hours later led to the biggest improvements in the risks of heart disease and type 2 diabetes. Eating after 9pm was linked to a 13 per cent increased risk of heart disease.

(This is probably because it works better with your body-clock rhythms, and the production of hormones such as insulin.)

so I’d recommend you avoid late-night eating (try to stop two to three hours before bed), aim for a 12 to 14-hour ‘fasting’ window, and stick to a nutritious Mediterranean-style diet.