Intermittent fasting could increase risk of cardiovascular death, flags study

19 Mar 2024 --- A new preliminary study involving people following a type of intermittent fasting eating schedule, finds that participants have a 91% higher risk of death from cardiovascular disease compared to those eating across the standard 12 to 16 hours per day.

“Restricting daily eating time to a short period, such as eight hours per day, has gained popularity in recent years as a way to lose weight and improve heart health,” says senior study author Victor Wenze Zhong, Ph.D., a professor and chair of the department of epidemiology and biostatistics at the Shanghai Jiao Tong University School of Medicine in Shanghai, China.

“However, the long-term health effects of time-restricted eating, including the risk of death from any cause or cardiovascular disease, are unknown.”

Those eating in a time-restricted eating schedule of eight hours or less were shown to have a higher risk of cardiovascular disease than those following a regular eating pattern. 

“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 to 16 hours per day, a shorter eating duration was not associated with living longer,” Zhong adds.

The analysis conducted in China was presented at yesterday’s American Heart Association (AHA) scientific session held in Chicago, US, and is yet to be peer-reviewed or published in a journal. 

The long-term health effects of time-restricted eating remain  unknown, despite the rise in popularity.Short-term benefits, long-term drawbacks
The study included approximately 20,000 adults residing in the US with an average age of 49 years. The participants were monitored for eight years, with a maximum monitoring span of 17 years.

Those included in the study were existent participants in the US National Health and Nutrition Examination Survey. They were at least 20 years old at enrollment, which took place between 2003 and 2018, and completed two 24-hour dietary recall questionnaires within their first year of enrollment. The study is based on self-reported dietary information. 

The researchers also presented preliminary data suggesting that this type of eating pattern increased the risk of cardiovascular death in people with heart disease or cancer.

Among those with pre-existing cardiovascular issues, an eating interval shorter than ten hours was associated with a 66% higher risk of death from heart disease or a stroke. There was no evidence that time-restricted eating contributes to reducing the overall risk of death from any cause. 

“It’s crucial for patients, particularly those with existing heart conditions or cancer, to be aware of the association between an eight-hour eating window and increased risk of cardiovascular death. Our study’s findings encourage a more cautious, personalized approach to dietary recommendations, ensuring that they are aligned with an individual’s health status and the latest scientific evidence,” Zhong explains.

Nonetheless, Zhong notes that more research into this area is needed to examine the biological mechanisms underlying the link between time-restricted waiting and adverse cardiovascular outcomes. 

He elaborates: “Although the study identified an association between an eight-hour eating window and cardiovascular death, this does not mean that time-restricted eating causes cardiovascular death.”

Christopher D. Gardner, Ph.D., Rehnborg Farquhar professor of Medicine at Stanford University, US and chair of the writing committee for the AHA 2023 scientific statement, comments: “When the study is presented in its entirety, it will be interesting and helpful to learn more of the details of the analysis.” 

“One of those details involves the nutrient quality of the diets typical of the different subsets of participants. Without this information, it cannot be determined if nutrient density might be an alternate explanation to the findings that currently focus on the window of time for eating. Second, it needs to be emphasized that categorization into the different windows of time-restricted eating was determined on the basis of just two days of dietary intake,” he adds.

“It will also be critical to see a comparison of demographics and baseline characteristics across the groups that were classified into the different time-restricted eating windows — for example, was the group with the shortest time-restricted eating window unique compared to people who followed other eating schedules, in terms of weight, stress, traditional cardiometabolic risk factors or other factors associated with adverse cardiovascular outcomes?”

Intermittent fasting has also been associated with the risk of developing an eating disorder. 

By Milana Nikolova