Intermittent fasting tied to 91% higher risk of cardiovascular death: Study

A recent study presented at an American Heart Association conference suggests that people who restrict their eating to less than 8 hours a day might be at a higher risk of cardiovascular disease. This research, still in its preliminary stages, involved over 20,000 adults in the United States. They found that participants who followed a time-restricted eating plan, a type of intermittent fasting, had a greater chance of dying from heart-related issues compared to those who spread their meals out over 12 to 16 hours.

Time-restricted eating involves limiting your food intake to a specific window within a 24-hour day. This window can vary from just 4 hours to 12 hours. A popular approach is the 16:8 method, where you eat all your meals within 8 hours and fast for the remaining 16 hours. Interestingly, previous studies have shown that time-restricted eating can actually improve certain heart health markers, like blood pressure, blood sugar, and cholesterol levels. However, this new research suggests there might be downsides to consider, particularly for heart health if you restrict your eating window too much.

“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,” said senior study author Victor Wenze Zhong, PhD, 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 the risk of death from any cause or cardiovascular disease, are unknown.”

This study investigated the long-term health effects of restricting your eating window to 8 hours per day. Researchers looked at dietary patterns of participants in a National Health Survey (NHANES) from 2003 to 2018 and compared it with death data from the same period.

The results were surprising. People who only ate within an 8-hour window had a significantly higher risk of dying from heart disease, compared to those who ate within a typical 12-16 hour window. This increased risk was even stronger for people who already had heart disease or cancer. Interestingly, those with existing heart disease who ate for slightly longer (8-10 hours) also had a higher risk of death from heart disease or stroke. The lead researcher emphasized that while 8-hour time-restricted eating may have been popular for short-term benefits, this study suggests it is not a healthy approach for long-term well-being. “We were surprised to find that 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, 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.

This study examined the dietary habits of a large group of adults in the United States. Researchers followed nearly 20,000 participants for an average of 8 years, with some being tracked for as long as 17 years.  The study focused on individuals who were at least 20 years old when they enrolled between 2003 and 2018. To ensure accurate dietary data, participants had to complete two detailed questionnaires about what they ate over a 24-hour period within the first year of the study.

The participants were a diverse group, with roughly equal numbers of men and women. In terms of race and ethnicity, the majority (73.3%) identified as non-Hispanic white, followed by Hispanic adults (11%), non-Hispanic Black adults (8%), and a smaller group (6.9%) who identified as mixed-race or another non-Hispanic race.

“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, Ph.D., FAHA, the Rehnborg Farquhar Professor of Medicine at Stanford University in Stanford, California.

“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 emphasised that categorisation into the different windows of time-restricted eating was determined based on 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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