Intermittent fasting linked to a higher risk of heart disease death

Restricting your eating window to just 8 hours a day, a popular type of intermittent fasting, has been linked to a higher risk of dying from heart disease. But some scientists argue that people with pre-existing health conditions may unknowingly opt for intermittent fasting if their symptoms or treatments affect their appetite and the quality of our diet is probably more important than when we eat.

Time-restricted eating has previously been linked to improved blood pressure, blood glucose and cholesterol levels, but its long-term effects are unclear.

To learn more, Wenze Zhong at the Shanghai Jiao Tong University in China and his colleagues studied around 20,000 adults, roughly evenly split between men and women, who participated in the US National Health and Nutrition Examination Survey. Their average age was 49 and just under three-quarters of them were non-Hispanic white people.

Every year from 2003 to 2018, the survey’s participants self-reported their dietary information. The researchers then matched this against the death records between 2003 to 2019 from the US Centers for Disease Control and Prevention. Participants were only included if they were aged 20 or older and had completed two diet questionnaires within their first year of the survey.

Over an average follow-up period of eight years, the team found that those who ate during an 8-hour daily window didn’t live longer than those with a more traditional eating schedule of 12 to 16 hours, despite intermittent fasting often being lauded for its longevity benefits.

The researchers also found that those who followed an 8-hour eating schedule were 91 per cent more likely to die from heart disease over the follow-up period than those who ate over 12 to 16 hours.

For those diagnosed with heart conditions before the study, eating over an 8 to 10-hour window was linked to a 66 per cent higher risk of death from heart disease compared with those who ate over 12 to 16 hours. Among those diagnosed with cancer, eating over a window of more than 16 hours was associated with a lower risk of death from the condition than a more constricted eating schedule.

The study – presented at the American Heart Association (AHA) Epidemiology and Prevention conference in Chicago – doesn’t prove that time-restricted eating caused any of these deaths, says Zhong.

It is important to consider the participants’ reasons for practising time-restricted eating, says Benjamin Horne at the Intermountain Heart Institute in Salt Lake City, Utah. Some might have adopted this pattern intentionally, while others could have had limited eating windows due to health conditions or treatments that affected their appetite, he says.

Some may have also had a restricted eating schedule because of limited access to food, says Jo Ann Carson, former chair of the AHA nutrition committee. Research suggests that food insecurity is associated with unhealthy lifestyles that lead to heart disease. “We also know nothing about the healthfulness of the foods they ate,” says Carson.

In their paper, the authors acknowledge their research relied on self-reported dietary information that may be inaccurate. They plan to investigate if the findings apply to people of a broader range of ethnicities and how fasting might increase the risk of harmful health outcomes.

People who want to reduce their likelihood of dying prematurely “should aim for an overall heart-healthy dietary pattern, regardless of the time of day they eat”, says Carson. Those who wish to start intermittent fasting should speak to their doctor beforehand, says Horne.