8-hour time-restricted eating linked to a 91% higher risk of cardiovascular death

A form of intermittent fasting called time-restricted eating entails setting aside a certain number of hours each day for eating, typically four to twelve hours total in a 24-hour period. The researchers observed that many people who adhere to a time-restricted eating plan have a 16:8 eating schedule, in which they fast for the remaining 16 hours of each day and consume all of their meals during an 8-hour window. Time-restricted eating has been shown to enhance blood pressure, blood glucose, cholesterol, and other cardiometabolic health indicators.

New preliminary research presented at the American Heart Association’s Epidemiology and Prevention Lifestyle and Cardiometabolic Scientific Sessions 2024, March 18–21, in Chicago, found that people who restricted their eating to less than 8 hours per day, a time-restricted eating plan, were more likely to die from cardiovascular disease compared to people who ate 12–16 hours per day. The analysis covered over 20,000 adults in the United States.

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, said, “Restricting daily eating time to a short period, such as 8 hours per day, has gained popularity in recent years as a way to lose weight and improve heart health. However, the long-term health effects of time-restricted eating, including the risk of death from any cause or cardiovascular disease, are unknown.”

In this study, researchers investigated the possible effects of an 8-hour time-restricted eating regimen on long-term health. They compared data from the Centers for Disease Control and Prevention’s National Death Index database, which contains information on deaths in the United States from 2003 to December 2019, with information regarding dietary patterns for participants in the annual 2003–2018 National Health and Nutrition Examination Surveys (NHANES).

The investigation discovered:

• Individuals who consumed all of their food in less than eight hours each day were 91% more likely to die from heart disease.
• Individuals with cancer or heart disease also had a higher risk of cardiovascular death.
• Eating for at least eight hours a day, but not more than ten was linked to a 66% increased risk of dying from heart disease or stroke in those who already had cardiovascular disease.
• Eating within a time constraint did not lower the chance of dying for any reason overall.
• Over 16 hours of eating per day has been linked to a decreased risk of cancer-related death in cancer patients.

It was surprising for scientists to find people who followed an 8-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, this 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, “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. Our study’s findings encourage a more cautious, personalized approach to dietary recommendations, ensuring they align with an individual’s health status and the latest scientific evidence. Although the study identified an association between an 8-hour eating window and cardiovascular death, this does not mean that time-restricted eating caused cardiovascular death.”

• The study included about 20,000 adults in the United States, with an average age of 49.
• Participants in the study were tracked for a maximum of 17 years and a median of 8 years.
• The study included information from NHANES participants who completed two 24-hour food recall questionnaires during their first year of participation and were at least 20 years old when they enrolled between 2003 and 2018.
• Of the participants, around half identified as men and the other half as women. In terms of self-identification, 73.3% of participants identified as non-Hispanic white adults, 11% as Hispanic adults, 8% as non-Hispanic Black adults, and 6.9% of adults as members of other racial categories, which included mixed-race adults and adults of other non-Hispanic races. 

One of the study’s limitations was that it relied solely on participant-reported dietary data, which could be influenced by memory or recollection and might not accurately represent regular eating patterns. The analysis excluded variables that might also impact health but were not related to the amount of food consumed daily or the reason for death.

The authors pointed out that future studies might investigate the biological mechanisms underlying the links between a time-restricted eating schedule and poor cardiovascular outcomes and whether these findings hold for individuals living in different parts of the world.

“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, Ph.D., FAHA, the Rehnborg Farquhar Professor of Medicine at Stanford University in Stanford, California, and chair of the writing committee for the Association’s 2023 scientific statement, Popular Dietary Patterns: Alignment with American Heart Association 2021 Dietary Guidance.

“One of those details involves the nutrient quality of the diets typical of the different subsets of participants. With this information, it can be determined if nutrient density might be an alternate explanation to the current findings on the time window 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.”