A 5-day high-caloric diet triggered liver fat accumulation and disrupted brain insulin action in men with a healthy body weight, with effects persisting even after resuming a normal diet. Researchers postulated that brain insulin responsiveness may adapt to dietary changes before weight gain, potentially facilitating the development of obesity.

"We show that short-term overeating with commonly used ultra-processed high-caloric snacks can trigger liver fat accumulation and short-term disrupted brain insulin action that outlast the timeframe of the HCD [high-caloric diet] in men," the study authors wrote.

This study was led by Stephanie Kullmann, PhD, Institute for Diabetes Research and Metabolic Diseases, Helmholtz Center Munich, University of Tübingen, Tübingen, Germany. It was published online in Nature Metabolism.

The small sample size was a major limitation of this study. Whole-body insulin sensitivity was not assessed using the gold standard method (hyperinsulinemic-euglycemic clamp). The study investigated male participants exclusively, making it unclear whether the findings extend to women, particularly given known sex-specific findings of insulin action on appetite, metabolism, and memory that depend partly on the menstrual cycle.

The studies received partial support through a grant from the Federal Ministry of Education and Research to the German Center for Diabetes Research and a grant from the State of Brandenburg. One author reported receiving research grants and lecture fees from and having other ties with many pharmaceutical companies.