At a time when intermittent fasting has become a much preferred and viable option for weight loss, eight-hour time-restricted eating or intermittent fasting might be the reason for a 91% higher risk of cardiovascular death, according to a study by the American Heart Association.

The study, which was conducted on more than 20,000 adult US individuals, with an average age of 49 years, says that people who limited their eating to less than eight hours per day were more likely to die from cardiovascular disease compared to people who ate across 12-16 hours per day.

"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 risk of death from any cause or cardiovascular disease, are unknown," says Victor Wenze Zhong, senior study author chair of the department of epidemiology and Biostatistics at the Shanghai Jiao Tong University School of Medicine in Shanghai, China.

According to Zhong, while the study identified an association between the eight-hour-long eating window and cardiovascular death, there is no evidence that says time-restricted eating is the cause of cardiovascular death. “Overall, this study suggests that time-restricted eating may have short-term benefits but long-term adverse effects,” says Christopher D. Gardner, Ph.D., FAHA, the Rehnborg Farquhar Professor of Medicine at Stanford University in Stanford, California.

Time-restricted eating is a form of intermittent fasting that limits the hours for food intake to a specific number of hours each day. The restricted time may range from a 4 -12 hour time window to 24 hours. With the growing popularity of intermittent fasting, many people follow a 16:8 eating schedule, where they eat food in an 8-hour window and fast for the remaining 16 hours each day.

The study also highlights that individuals with prior heart conditions have an increased risk of cardiovascular disease. Among people with existing cardiovascular disease, an eating duration of no less than 8 but less than 10 hours per day was also associated with a 66% higher risk of death from heart disease or stroke, as per the study. 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. “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,” says Zhong.

Notably, the study limits the inclusion of nutrient quality of the diets and other factors such as stress, demographic, cardiometabolic risk factors and other factors associated with adverse cardiovascular outcomes.

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