People who fast for 16 or more hours per day are more at risk of having a stroke or heart attack in later life, new evidence indicates.

Individuals who only eat during an eight-hour period of the day are more likely to die from a heart problem compared to those who consume food throughout the entire day, latest research has identified.

In recent years, time-restricted eating has soared in popularity after some well-known figures have announced they fast for long periods, such as Jennifer Aniston, Elon Musk and Rishi Sunak.

Prior research has found that fasting can improve an individual’s cholesterol, blood pressure and blood glucose levels.

However, a new study looking at 20,000 adults has discovered that the participants who followed a time-restricted eating diet were 90% more likely to die from heart disease compared to those on another diet.

During the review, the team of academics looked at diet information from annual health surveys between 2003-2018. They then compared it to death data over the same period.

The majority of people who follow a time-restricted eating diet fast for 16 hours and eat for the remaining eight.

People on 16:8 diet most at risk

According to the results, people on the 16:8 diet were more at risk of dying from heart disease compared to those consuming food during 12- and 16-hour windows.

The team of researchers stated: “Those with existing heart disease or cancer were particularly at risk.”

Author Professor Victor Wenze Zhong said: “We were surprised to find that people who followed an eight-hour, time-restricted eating schedule were more likely to die from cardiovascular disease.

“Even though this type of diet has been popular due to its potential short-term benefits, our research clearly shows that, compared with a typical eating time range of 12-16 hours per day, a shorter eating duration was not associated with living longer.”

Other possible contributory factors were not considered at the start of the observational research study, such as the participant’s cholesterol level and weight.

Keith Frayn, Emeritus Professor of Human Metabolism at Oxford University, commented: “Time-restricted eating is popular as a means of reducing calorie intake, although its proponents claim other benefits such as ramping up metabolism.

“This work is very important in showing that we need long-term studies on the effects of this practice. But this abstract leaves many questions unanswered, and further research will be needed.”

Tom Sanders, Emeritus Professor of Nutrition and Dietetics at King’s College London, added: “Although popular, there is little evidence to show fasting benefits weight loss or weight maintenance.

“We know from previous existing evidence that it is probably better to spread food intake out throughout the day – small but often – rather than consume large meals over a shorter period.

“This is because large increases in blood fats and glucose result after big meals.”

That said, the study’s reliance on self-reported data introduces additional uncertainties as accurately recalling and reporting dietary habits is notoriously challenging.

Not so fast: is this a quality study?

The research was presented at an American Heart Association conference and used data from the National Health and Nutrition Examination Survey (NHANES).

The research had not undergone peer review, which means it had not been assessed by experts in the field.

Critics of the study argue that many participants might not have been intentionally been practicing time-restricted eating.

Instead, they suggest participants may have been eating over shorter periods due to other factors like poor appetite or illness which could also affect heart disease risk.

Observational studies by their nature identify correlations but are limited in their ability to control for all potential confounding variables.

This research highlights the complexity of dietary studies and the need for randomised controlled trials (RCTs) which can better understand the causal effects of intermittent fasting.

RCTs which compare specific interventions while controlling for various external factors have consistently demonstrated intermittent fasting’s benefits for weight loss and heart disease risk factors.

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