Intermittent fasting ‘could raise risk of fatal heart disease’

 source: the Times

Scientists tracking 20,000 people find higher cardiovascular risk in those who eat only in an eight-hour window

 

Diets in which people eat only during an eight-hour daily window and fast for the rest of the day may be linked to an increased risk of death from heart attacks and strokes, scientists have claimed.

Intermittent fasting has been endorsed by celebrities including Jennifer Aniston, Hugh Jackman, Kourtney Kardashian and Scarlett Johansson.

Research has linked it to short-term improvements in blood pressure, blood sugar and cholesterol.

However, long-term outcomes have now been explored in one of the first studies of its kind. After tracking about 20,000 adults in the United States, it found that those who said they ate within an eight-hour window were nearly twice as likely to die of heart attacks or strokes, compared with those who said they spread meals and snacks across 12 to 16 hours.

The researchers stressed that the results must be treated with caution, as this kind of study cannot prove cause and effect. They also had very limited information on the participants’ eating habits.

One limitation was that the volunteers who took part were only asked about their eating patterns on two days, and it was assumed that they followed the same schedule for several years. However, other experts said follow-up studies would be valuable as the “striking” results challenged widely held assumptions.

“We had expected that long-term adoption of eight-hour time-restricted eating would be associated with lower risk of cardiovascular death,” said Professor Victor Wenze Zhong of the Shanghai Jiao Tong University School of Medicine, senior author of the research. “We were surprised to find that compared to people whose eating duration was 12 to 16 hours, those who restricted their eating time to within eight hours per day had higher risk of cardiovascular death and did not live longer.”

He said his team had controlled for factors that might have skewed the results, such as the age of the participants, as well as income, body mass index, smoking, drinking and blood pressure. However, it is still possible that something other than the timing of meals was behind the effect.

Duane Mellor, a senior lecturer at Aston Medical School in the UK who was not involved in the study, said that some people, including night shift workers, were forced to eat at certain times. “Some people might be doing this [time-restricted eating] for health reasons [which may mean they were in worse shape to start with], while for others it’s due to stressful work environments or poverty, which are both risk factors for cardiovascular death,” Mellor said.

Christopher Gardner, a professor of medicine at Stanford University in California who was also not part of the research, agreed that more work was needed. He said: “Overall, this study suggests that time-restricted eating may have short-term benefits but long-term adverse effects.”

One theory would be that people eat fewer calories but continue eating junk food. “The short window of time-restricted eating … may help people cut back on calories and lose weight. However, if the calories that are being consumed are of low dietary quality, this might possibly lead to long-term adverse outcomes,” Gardner added.

Zhong told The Times his team had observed that people who reported eating in an eight-hour period had less lean muscle mass. “Loss of lean body mass has been linked to higher risk of cardiovascular mortality,” he said. “Other mechanisms linking eight-hour time-restricted eating with cardiovascular morality require further investigations. This will be an exciting research question, but we really do not know much right now.”

The study looked at about 20,000 adults with an average age of 49 when it began. They were tracked for as long as 17 years, and for a median of eight years; 840 died of heart attacks and strokes.

Those who reported eating all their food across less than eight hours a day had a 91 per cent higher risk of death from these cardiovascular causes, according to results due to be presented to a conference of the American Heart Association in Chicago this week.

Time-restricted eating did not reduce the overall risk of death from any cause. “Our study’s findings encourage a more cautious, personalised approach to dietary recommendations,” Zhong said.

Behind the story

Not so fast: if you feel the benefits, don’t ditch the diet just yet

By Rhys Blakely

Besides being endorsed by a multitude of celebrities, fasting diets have this going for them: people seem to find them relatively easy to stick to.

You can typically eat whatever you want, with no limits on calories, as long as meals are restricted to certain times, say between 12pm and 8pm.

Studies have suggested that people can lose weight by following these rules, probably because they end up consuming less food, and that they can help patients with type 2 diabetes control blood sugar levels.

One piece of research found that healthy men who fasted during the Islamic holy month of Ramadan, for about 16 hours a day, had an altered gut microbiome by the end, with higher levels of a beneficial bacterium that has been linked with a lower risk of cancer and inflammatory bowel disease, and improved heart health and mental health. In another trial, fasting for 15 to 16 hours each day for a month led to lower blood pressure in patients whose readings had been dangerously high.

But these studies, while intriguing, had something in common: they found short-term outcomes in small numbers of participants.

The latest research is one of the first to try to explore what time-restricted eating might mean if people kept it up for many years. Its strengths are that it looked at a relatively large number of people and followed them for a long time (eight years was the median average). But it has important limitations, including that it has not yet been peer reviewed and that the 20,000 people who took part were only asked about when they ate for two days. We don’t know whether those who reported time-restricted eating continued with it throughout the study.

The participants were part of a national nutritional survey that is representative of the US population, notes Tom Sanders, professor emeritus of nutrition at King’s College London. But if they were regularly fasting, we don’t know if they’d made a voluntary choice to do so. “It is likely that individuals reporting time-restricted eating may be working anti-social hours (eg truck drivers, security personnel, health professionals, night workers). This is important because there is evidence that this type of working practice is associated with increased risk of type 2 diabetes and cardiovascular disease,” he said. It’s possible that some were put on strict diets by their doctors because they’d been in poor physical shape, which might explain why they were more likely to die of heart attacks and strokes.

It is also plausible that for avoiding cardiovascular disease, many small meals really are better than a few large ones. “Large increases in blood fats and glucose result after big meals,” Sanders said. These postprandial surges can damage the lining of blood vessels and increase the level of blood clotting factors, he added.

For now, though, there’s no solid evidence to say you should ditch intermittent fasting if it’s helping you to maintain a healthy weight and you feel good doing it. It can be exasperating to hear scientists conclude that more research is needed, but in this case it’s true.

 

 

 

 

 

Fasting for 24 hours between meals could lower diabetes risk

 

Regular periods of fasting where you leave 24 hours between meals could reduce your risk of diseases such as diabetes and Alzheimer’s, a Cambridge study suggests.

Researchers have found that leaving a full day between meals can reduce levels of harmful inflammation in the body by boosting production of a key fatty acid, suggesting that routine fasting sessions could boost your health.

Fasting diets have grown in popularity in recent years, with claims that they are effective as a means of weight loss, as a way of keeping the body’s cells healthy, and even as a way of boosting productivity.

It emerged this week that the prime minister, Rishi Sunak, fasts for 36 hours at the start of every week as part of a “balanced lifestyle”, arguing that it then allows him to indulge his “weakness for sugary things” for the rest of the week.

It has long been suspected that the human body is not well suited, in evolutionary terms, to the modern habit of constant snacking and grazing throughout the day. Instead, it is thought that our bodies are better adapted to the dietary routine of our hunter-gatherer ancestors, who were likely to have eaten fewer meals with much longer gaps in between.

 

the rest of the article @ The Times, here.

 

“We’re very interested in trying to understand the causes of chronic inflammation in the context of many human diseases, and in particular the role of the inflammasome [molecules that activate inflammatory responses],” said Clare Bryant from Cambridge’s department of medicine.

“What’s become apparent over recent years is that one inflammasome in particular — the NLRP3 inflammasome — is very important in a number of major diseases such as obesity and atherosclerosis, but also in diseases like Alzheimer’s and Parkinson’s diseases, many of the diseases of older-age people, particularly in the western world.”

 

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Scientists wanted to find out why fasting seems to reduce inflammation. They studied a group of 21 volunteers, asking them to eat a 500-calorie meal, fast for 24 hours, and then eat another 500-calorie meal.

The results, published in the journal Cell Reports, found that this 24-hour fast increased the levels of a fatty acid called arachidonic acid. These levels then dropped again once the participants ate another meal.

The researchers tested the effect of this acid on immune cells in a laboratory and found that arachidonic acid reduced the activity of the NLRP3 inflammasome linked with harmful inflammation.

“This provides a potential explanation for how changing our diet — in particular by fasting — protects us from inflammation, especially the damaging form that underpins many diseases related to a western high-calorie diet,” Bryant said.