Intermittent fasting, a widely practiced approach for weight management by restricting food consumption to specific time frames, faces scrutiny following an unexpected discovery from research presented at a medical conference.

The study, unveiled in Chicago, revealed a surprising 91% increase in the risk of heart disease-related mortality associated with confining meals to an eight-hour daily window. The American Heart Association released only an abstract, leaving scientists speculating about the study’s methodology. Prior to its release, the study underwent scrutiny by other experts, as stated by the AHA.

Lifestyle interventions aimed at weight loss are being scrutinized amidst the emergence of new drugs aiding weight reduction. Some medical professionals questioned the study’s findings, suggesting potential biases due to discrepancies, such as underlying heart health, between the fasting group and the comparison group, who consumed food over a daily period of 12 to 16 hours.

Keith Frayn, emeritus professor of human metabolism at the University of Oxford, emphasized the popularity of time-restricted eating as a method for reducing calorie intake. He underscored the significance of conducting long-term studies to understand its effects fully, noting that the current abstract raises numerous unanswered questions.

Led by Victor Zhong from the Shanghai Jiao Tong University School of Medicine, researchers examined data from approximately 20,000 adults included in the US Centers for Disease Control and Prevention’s National Health and Nutrition Examination Survey. The study analyzed responses to questionnaires and mortality data spanning from 2003 to 2019. However, reliance on self-reported dietary information raised concerns about potential inaccuracies, given that participants had to recall their food intake over two days.

The duration of intermittent fasting among participants remained unclear, although researchers assumed its continuity, according to Zhong. Fasting individuals tended to be younger men with a higher BMI and food insecurity, with lower rates of hypertension, diabetes, and cardiovascular disease based on self-reports. Zhong highlighted that despite controlling for these factors in the analysis, a positive association between eight-hour time-restricted eating and cardiovascular mortality persisted.