Intermittent Fasting Warning: 8-Hour Eating Window Linked To 91% Higher Risk Of Death From Heart Disease

CHICAGO — Intermittent fasting is a growing dietary trend embraced by health-conscious individuals who hope to improve their overall health and lifespan. New research, however, warns that one common form of the diet may actually worsen health down the road. Scientists say restricting your eating in an eight-hour time frame may significantly increase the risk of dying from cardiovascular disease, challenging previous beliefs about the diet’s heart health benefits.

Time-restricted eating is a form of intermittent fasting that confines daily eating to a set number of hours, often seen in the 16:8 method, where all meals take place within an eight-hour period followed by 16 hours of fasting. Proponents have touted its benefits for improving various health markers, including blood pressure, blood sugar, and cholesterol levels, making it a popular form of dieting.

The large-scale study involving over 20,000 American adults was presented at the American Heart Association’s Epidemiology and Prevention│Lifestyle and Cardiometabolic Health Scientific Sessions 2024 in Chicago.

“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 Dr. Victor Wenze Zhong, a professor and chair of the department of epidemiology and biostatistics at the Shanghai Jiao Tong University School of Medicine in China, in a media release. “However, the long-term health effects of time-restricted eating, including risk of death from any cause or cardiovascular disease, are unknown.”

To assess these risks, researchers analyzed dietary patterns from the National Health and Nutrition Examination Surveys (NHANES) spanning 2003 to 2018, correlating these with mortality data up to December 2019. The study unveiled a startling 91-percent higher risk of cardiovascular mortality among individuals adhering to an eating window of less than eight hours compared to those who spread their meals across 12 to 16 hours.

This heightened risk was also observed in individuals with pre-existing heart disease or cancer. There was a 66-percent higher prospect of death from heart disease or stroke for those with an eating duration between eight to 10 hours daily. Researchers noted that eating over a period of more than 16 hours per day might reduce cancer mortality among those already diagnosed with the disease.

“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,” explains Dr. Zhong. “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’s participant pool was diverse, including roughly equal numbers of men and women, but had a significant majority identifying as non-Hispanic Whites. The research, however, acknowledges limitations such as reliance on self-reported dietary information and the absence of factors outside daily eating duration that could impact health.

Dr. Christopher D. Gardner, the Rehnborg Farquhar Professor of Medicine at Stanford University, emphasized the need for further research, particularly regarding the nutrient quality of diets within different eating windows and demographic comparisons among participants.

“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,” says Dr. Gardner, chair of the writing committee for the Association’s 2023 scientific statement — Popular Dietary Patterns: Alignment with American Heart Association 2021 Dietary Guidance.

This study points to the complex nature of diet and its impact on health, suggesting that while time-restricted eating may offer short-term benefits, its long-term effects deserve careful consideration and further study.