TV doctor defends diet loved by celebs as study claims it’s bad for your heart

TV doctor defends diet loved by celebs as study claims it’s bad for your heart

Doctor Michael Mosley has long hailed intermittent fasting as a diet and lifestyle that can not only help you lose weight, but as a way to reduce the risk of diabetes and have a healthier heart – but a study is now disputing those claims.

Intermittent fasting, or time restricted eating, means that you alternate between eating, and then going for extended periods of time without food. It’s not a novel concept, having been around for thousands of years.

It’s one of the major pillars of TV doctor Michael Mosley’s Fast 800 diet, which is based on a Mediterranean-style diet full of protein, fibre and healthy fats – as well as intermittent fasting. He also popularised the 5:2 diet, which involves eating normally for five days, and restricting the amount of food eaten the other two days.

This is an image of plate with food on it and two hands resembling those of a clock

Intermitting fasting involves eating during time-restricted periods (stock image)
Getty Images)

Dr Mosley has long been vocal about the apparent benefits of intermittent fasting, a diet style which has also been followed by stars such as Jennifer Aniston and Heidi Klum. According to the doctor, following this lifestyle can increase focus and improve decision-making, boost your immune system and lead to a healthier heart. It can also reduce the risk of diabetes and lower the hunger hormone, ghrelin, reducing the chance of obesity by 41 per cent.

But a recent study has now claimed that intermittent fasting can double the risk of dying from heart problems. According to the research, which was done by Shanghai University School of Medicine and hasn’t yet been peer-reviewed, people who limited their eating window to less than eight hours a day, had a whopping 91 per cent (almost double) increased risk of dying from heart and circulatory disease, compared to those who had a 12 to 16 hour eating window.

Among those who were already living with a cardiovascular disease, the study found those eating for more than eight, but less than 10 hours a day, was associated with a 66 per cent higher risk of death from heart disease or stroke. And it found time-restricted eating didn’t reduce the risk of dying, from any cause. The researchers studied 20,000 US adults, and an abstract was shared by the American Heart Association, but the full findings piece haven’t yet been published in a journal.

Dr Mosley has said he was “shocked and surprised” about the findings, but claimed that “experts are extremely sceptical about the study”. He pointed to the fact that there have been “100s of studies carried out on different forms of intermittent fasting over the last 10 years” and that they have “consistently shown that intermittent fasting can be hugely beneficial”.

For example, one piece of research into intermittent fasting, which was 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]”.

Dr Mosley claims the piece of research, which has not yet been published in a peer-reviewed journal, is “suspect”, and there are “several other reasons to be doubtful”. He said: “What the press release claims is that a new study 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 percent higher risk of death from cardiovascular disease.”

Explaining why he’s doubtful about the research, Dr Mosley said: “What the researchers did was pick out those who had ticked a box saying that on two particular days (across an 8 year study) they’d restricted their food consumption to an eight-hour window or less. The researchers then cross referenced these people to the US National Death Index database to see if they were more or less likely to live long and healthy lives.

“And it turned out, to everyone’s surprise, that those who ticked the box had almost twice the risk of dying from heart disease than people who hadn’t. The trouble is we don’t know anything about the people who ticked the box. How old were they? How healthy? How accurate are their recollections of when they ate? And why did the researchers just look at two days, across an 8 year period, and decide those were typical of what they did on all the other days?”

Quoting Kevin McConway, Emeritus Professor of Applied Statistics at the Open University, he added: “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.”

Dr Mosley also noted that the data is collected from people nearly 20 years ago, “at a time when no-one was talking about the health benefits of doing time restricted eating”. He added: “So, as other experts have pointed out, it is far more plausible that anyone eating that way, back then, was doing so because they had existing health problems (like cancer of heart disease) or because they were doing shift work (ie truck drivers, security guards etc), something which is strongly linked to an increased risk of heart disease and type 2 diabetes.”

In addition, Dr Mosley pointed out that the abstract doesn’t explain what the contributors ate during the eight-hour window. For example, was it mainly highly processed junk food, or was it a healthy, varied diet?

He concluded: “So, no, my belief in the benefits of intermittent fasting has not been shaken by this abstract, and nor should yours.”

According to the Mayo Clinic, intermittent fasting is about as effective as a typical low-calorie diet for weight loss. And when it comes to lowering risk of obesity-related diseases, it says it seems to “be about as beneficial as any other type of diet that reduces overall calories”. While intermittent fasting is safe for many people, it’s not recommended for everyone. If you considering it, speak to your GP.

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Kerri Waldron

My name is Kerri Waldron and I am an avid healthy lifestyle participant who lives by proper nutrition and keeping active. One of the things I love best is to get to where I am going by walking every chance I get. If you want to feel great with renewed energy, you have to practice good nutrition and stay active.