NATIONWIDE — An analysis of over 20,000 U.S. adults found that people who limited their eating to less than eight hours per day—aka a time-restricted eating plan—were more likely to die from cardiovascular disease compared to people who ate across 12-16 hours per day, according to preliminary research presented by the American Heart Association in March. 

Time-restricted eating, a type of intermittent fasting, involves limiting the hours for eating to a specific number of hours each day. This could range from a four to a 12-hour time window in a given 24-hour period. 

Many people who follow a time-restricted eating diet follow a 16:8 eating schedule, where they eat all their foods in an eight-hour window and fast for the remaining 16 hours each day, the researchers noted. 

Previous research has found that time-restricted eating improves several cardiometabolic health measures, such as blood pressure, blood glucose and cholesterol levels.

“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,” said 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 risk of death from any cause or cardiovascular disease, [were] unknown.”

So the researchers investigated. They reviewed information about dietary patterns for participants in the annual 2003-2018 National Health and Nutrition Examination Surveys (NHANES) in comparison to data about people who died in the U.S., from 2003 through December 2019, from the Centers for Disease Control and Prevention’s National Death Index database.

The analysis found:

People who followed a pattern of eating all of their food within 8 hours per day had a 91 percent higher risk of death due to cardiovascular disease.

The increased risk of cardiovascular death was also seen in people living with heart disease or cancer.

Among people with existing cardiovascular disease, an eating duration of a minimum of eight but less than 10 hours per day was also associated with a 66 percent higher risk of death from heart disease or stroke.

Time-restricted eating did not reduce the overall risk of death from any cause.

An eating duration of more than 16 hours per day was associated with a lower risk of cancer mortality among people with cancer.

“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,” 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,” he continued. “Although the study identified an association between an eight-hour eating window and cardiovascular death, this does not mean that time-restricted eating caused cardiovascular death.”

The study’s limitations included its reliance on self-reported dietary information, which could be affected by a participant’s memory or recall and might not accurately assess typical eating patterns. Factors that could also play a role in health were not included in the analysis.

Future research might examine the biological mechanisms that underly the associations between a time-restricted eating schedule and adverse cardiovascular outcomes, and whether these findings are similar for people who live in other parts of the world, the authors noted.

“Overall, this study suggests that time-restricted eating may have short-term benefits but long-term adverse effects. When the study is presented in its entirety, it will be interesting and helpful to learn more of the details of the analysis,” said Christopher D. Gardner, the Rehnborg Farquhar Professor of Medicine at Stanford University in Stanford, CA. 

“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 said.

“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? This additional information will help to better understand the potential independent contribution of the short time-restricted eating pattern reported in this interesting and provocative abstract.”

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