I was 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 ‘autophagy, a form of cellular ‘spring cleaning’, where old cells are broken down and recycled.
Dr Michael Mosley was puzzled by research which suggests following a 16:8 pattern of time-restricted eating is linked to a 91 per cent higher risk of death from cardiovascular disease
A review of all the best research, published in the New England Journal of Medicine in 2019, concluded that ‘intermittent fasting has broad-spectrum 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 time-restricted eating (fasting for 16 hours and eating during an eight-hour 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The so-far unpublished study, by researchers from the Shanghai Jiao Tong University School of Medicine, looked at data from the U.S. National Health and Nutrition Examination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 Chinese researchers did was pick out those who had ticked a box saying that on two days they’d restricted their food consumption to an eight-hour window or less. The researchers then cross-referenced these people to the U.S. National Death Index database to see what happened to them.
It turned out that these intermittent fasters 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, 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, 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 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 risk of heart disease and risk of 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 diet.
Scan could spot different types of bowel cancer faster
The good news is that thanks to screening and new treatments, survival rates from most cancers have shot up.
Unfortunately the rates of some cancers are still rising, particularly in younger groups. One of the most striking examples is bowel cancer. A recent paper in the journal Annals of Oncology predicted that deaths from bowel cancer in young people in the UK this year will be 26 per cent higher in men and nearly 39 per cent higher in women than they were in 2018.
The researchers from the University of Milan blame surging rates of obesity, alongside heavy alcohol drinking and low physical activity. But sometimes, of course, it is just bad luck. The best way to protect yourself is to catch it early, so if you’ve been sent a home test by the NHS (in England it’s offered to those aged 60-plus, though soon all over-50s will be eligible), then use it.
The test involves collecting a small sample of poo and sending it to a lab where they check it for tiny amounts of blood. If it shows signs of blood, you’ll be referred for a colonoscopy to examine inside your bowel (and then possibly a biopsy). I’ve had this done, and while it’s an important test, I can’t say I enjoyed the process.
And so I was pleased to see new research by the University of Glasgow showing that in future it may be possible to use a PET scan in place of doing a biopsy. This showed that PET scans can accurately diagnose different types of bowel cancer faster, which could help match patients to the best treatment for them.
Another bit of good news is that researchers at the Massachusetts Institute of Technology have discovered how early colon cancers manage to evade our immune system.
They do this by making a protein, SOX17, which is normally produced by a foetus to protect itself from being attacked by its mother’s immune system. Due to a mutation, bowel cells start to make it, too — if scientists can find a way to block SOX17, it could offer a new way to treat early-stage cancers.
For ethical and environmental reasons, I’m trying to cut back on the amount of meat I eat, and that has meant, along with tofu and lentils, I’ve been exploring meat substitutes, such as insects, which are packed with protein and fibre.
I’ve tried locusts, grasshoppers and mealworms, all of which were OK. But what about eating snakes?
A recent study by Macquarie University in Australia concluded that snakes are a great source of protein and more eco-friendly than eating beef or lamb.
That’s because cold-blooded reptiles are more efficient at turning the food they eat into protein than warm-blooded animals.
When I was last in China I was offered snake cooked in a stew. It did make me feel a bit squeamish, but it was tasty, a bit like chicken.
