Intermittent fasting may be associated with a higher risk of death, study says

A new study showed that people who adhere to a type of intermittent fasting they had a 91% higher risk of death from cardiovascular disease . The findings were presented in Epidemiology and Prevention | Lifestyle and Cardiometabolic Scientific Sessions 2024, from American Heart Associationthis Monday (18).

Intermittent fasting is a strategy based on consume all meals of the day within a time window It is spend most of the day fasting . The study in question analyzed 20,000 adults in the United States and found that people who limited their diet less than 8 hours a day (i.e., they ate only during this period) had more likely to die from cardiovascular disease compared to people who ate at regular intervals (12 to 16 hours a day).

In intermittent fasting, many people follow a diet with schedule 16:8 , where they eat all their food within an 8-hour window and fast for the remaining 16 hours, every day. Some previous studies have shown that this type of diet could bring health benefits, such as improving blood pressure, reducing blood glucose and cholesterol.

“Restricting daily eating time to a short period, such as 8 hours a day, has gained popularity in recent years as a way to lose weight and improve heart health,” said study senior author Victor Wenze Zhong, professor and chairman of the department of epidemiology and biostatistics, Shanghai Jiao Tong University School of Medicine, Shanghai, China.

“However, the long-term health effects of time-restricted eating, including the risk of death from any cause or cardiovascular disease, are unknown.”

How was the study carried out and what results were found?

For the study, researchers investigated the potential long-term health impact of following intermittent fasting with an 8-hour eating window. To do this, they reviewed information on dietary patterns for participants in the 2003-2018 annual National Health and Nutrition Examination Surveys (NHANES) in the United States and compared it with data on people who died in the US between 2003 and 2019, available on CDC (National Center for Disease Control and Prevention) Death Index database.

Study participants were followed for an average of 8 years, with a maximum follow-up period of 17 years. Adults were at least 20 years old at the time of enrollment in NHANES and completed two dietary questionnaires in the first year of enrollment. Approximately half of the participants identified as men and half identified as women.

Among the results of the analysis are:

• People who followed a diet with restrictions on meals less than 8 hours a day had a 91% higher risk of death due to cardiovascular disease;
• Increased risk of cardiovascular death has also been seen in people living with heart disease or cancer;
• In people with cardiovascular disease, eating more than 8 hours but less than 10 hours a day was also associated with a 66% higher risk of death from heart disease or stroke;
• Time-restricted feeding did not reduce the overall risk of death from any cause;
• An eating duration greater 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 a time-restricted 8-hour eating schedule were more likely to die from cardiovascular disease. Although this type of diet has been popular due to its potential short-term benefits, our research clearly shows that, compared to a typical eating time frame of 12-16 hours per day, a shorter feeding duration was not associated to a longer life,” says Zhong.

The study author also believes the findings encourage a more cautious and personalized approach to dietary recommendations, taking into account the patient's health status and the latest scientific evidence.

Study only points to relationship and not cause

However, the researcher emphasizes that the results of the study only show a relationship between intermittent fasting and death from cardiovascular disease . “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,” he says.

Future research could examine the biological mechanisms behind associations between time-restricted eating and adverse cardiovascular outcomes. Furthermore, it is also necessary to understand what other factors could be related to death from cardiovascular disease, such as weight, stress and other risk factors.

“One of these details involves the quality of nutrients in the typical diets of different subsets of participants [do estudo]. Without this information, it cannot be determined whether nutrient density can be an alternative explanation to findings that currently focus on the time window for eating,” says Christopher D. Gardner, Rehnborg Farquhar Professor of Medicine at Stanford University and president of the writing committee for the scientific declaration of the event at which the study was presented.