• Posted March 19, 2024

Could Intermittent Fasting Diets Raise Heart Risks?

Intermittent fasting might be bad for your heart, a new study warns.

People who restricted their eating to an 8-hour window had nearly twice the risk of heart-related death compared to folks who ate freely, results show.

This runs counter to previous research in which intermittent fasting improved several measures related to heart health, including blood pressure, blood sugar and cholesterol levels, the researchers noted.

“We were surprised to find that people who followed an 8-hour, time-restricted eating schedule were more likely to die from cardiovascular disease,” said senior researcher Victor Wenze Zhong, chair of epidemiology and biostatistics at the Shanghai Jiao Tong University School of Medicine in Shanghai.

“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,” Zhong added in an American Heart Association (AHA) news release.

For the study, Zhong and his colleagues analyzed data on more than 20,000 U.S. adults who participated in an annual federal survey on health and nutrition between 2003 and 2018. The survey tracked participants' pattern of eating.

Many people who adhere to time-restricted fasting tend to eat all their food in an 8-hour window, and then fast for the rest of the day, researchers said.

Comparing diet data to national death records, researchers found that people who tended to eat all their meals within an 8-hour span each day had a 91% higher risk of death from heart problems.

That increased risk also held among people already diagnosed with heart disease.

Among people with heart disease, restricting food intake to a 10-hour window was associated with a 66% higher risk of death from heart disease or stroke, researchers said.

“It's crucial for patients, particularly those with existing heart conditions or cancer, to be aware of the association between an 8-hour eating window and increased risk of cardiovascular death,” Zhong said. “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.”

Overall, time-restricted eating did not reduce a person's risk of death from any cause.

However, Zhong noted that the study wasn't designed to not prove a cause-and-effect link between intermittent fasting and heart-related death.

More research is needed to better understand why time-restricted eating might be harmful to heart health, Zhong said.

Christopher Gardner, a professor of medicine at Stanford University, said it will be important to track differences among people who are engaging in intermittent fasting.

“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 [heart] risk factors or other factors associated with adverse cardiovascular outcomes?” said Gardner, who was not involved in the study.

The new study was presented Monday at the American Heart Association's Epidemiology and Prevention scientific sessions in Chicago. Findings presented at medical meetings are considered preliminary until published in a peer-reviewed journal.

More information

Johns Hopkins Medicine has more about intermittent fasting.

SOURCE: American Heart Association, news release, March 18, 2024