Scientists dispute study linking time-restricted eating to poor heart health

08 Apr 2024 --- Researchers at the University of Chicago, US, are questioning the validity of a recent study publicized by the American Heart Foundation, which found that adults following an 8-hour time-restricted eating schedule had a 91% higher risk of death from cardiovascular death.

The preliminary study conducted at the Shanghai Jiao Tong University School of Medicine in Shanghai, China, included 20,000 US adults participating in the ongoing US National Health and Nutrition Examination Survey.

“The conclusions are extremely overstated considering that the investigators only have two days of dietary intake data over a 20-year period. What were the subjects eating on the other 7,300 days of the study? Two days of diet record data are not at all reflective of an individual’s regular eating pattern — this is a major limitation to the study,” Krista Varady, professor of kinesiology and nutrition at the University of Chicago, tells Nutrition Insight. 

Questionable conclusions
Varady, alongside Kelsey Gabel, assistant professor at the University of Chicago College of Applied Health Sciences and more than 30 other researchers in the field have drafted a commentary outlining the research errors in the Shanghai Jiao Tong University study.

“In addition, the researchers did not control for other important health variables in their analysis. For instance, a person’s alcohol consumption, physical activity level, smoking status, access to health care, level of stress and socioeconomic status greatly influence their risk of developing cardiovascular diseases,” she explains. 

Alcohol consumption, physical activity level, smoking status, access to health care, level of stress and socioeconomic status greatly influence risk of cardiovascular diseases.“Since the authors didn’t control for these critical factors, the overall conclusions of the paper are highly questionable.”  

The first example of a considerable flaw in the widely publicized study is the fact that it improperly adjusted the smoking status of participants. In it, there were 60% more smokers in the fasting group eating less than eight hours per day than the reference group. 

The two groups were also ethnically imbalanced, with 250% more black US citizens in the fasting group. This was unaccounted for despite the well-documented racial disparities in most causes of mortality in the US. 

Another potential issue with the study is that the method used to define eating duration is not representative of long-term eating patterns. Not only were these habits evaluated based on data collected at a single time point during two days of dietary recall, the eating times of less than eight hours commonly represented incomplete food records rather than a true short eating window. 

In contrast, the researchers opposing the controversial study point to over 100 published peer-reviewed clinical trials, which find that time-restricted eating can have small to larger metabolic health benefits, with no studies observing serious adverse effects of fasting. 

Studies have also shown intermittent fasting to lower overall disease risk and biological age, and neurodegenerative diseases, such as Alzheimer’s.

By Milana Nikolova