Fasting Doesn’t Impair Cognitive Function in Adults, New Meta-Analysis Finds

A comprehensive new analysis of decades of research indicates that intermittent fasting or time-restricted eating does not negatively impact cognitive performance in healthy adults, challenging long-held beliefs about the brain’s need for constant fuel.

Researchers conducted a meta-analysis of 71 independent studies, encompassing data from 3,484 participants and 222 cognitive tests spanning from 1958 to 2025. The findings, released today, revealed no significant difference in attention, memory, or executive function between individuals who had recently eaten and those who were fasting. This research arrives as intermittent fasting gains popularity as a wellness practice, with many seeking its potential health benefits.

However, the study did identify key factors influencing cognitive effects. Age proved crucial, with children and adolescents exhibiting poorer test results when fasting, suggesting their developing brains are more sensitive to energy fluctuations. Longer fasting periods were associated with a smaller performance gap, potentially due to the body’s metabolic shift to using ketones for fuel. Furthermore, performance dipped when tests were administered later in the day, and when tasks involved food-related cues. As one researcher noted, “Hunger doesn’t create universal brain fog, but it does make us more easily distracted when food is on our minds.” For more information on metabolic flexibility, see Healthline’s guide to metabolic flexibility.

The research team emphasized that fasting is not a universal solution and caution is advised for children, teens, and individuals with medical conditions. “Ultimately, fasting is best seen as a personal tool rather than a universal prescription,” the study concludes. Understanding the impact of diet on brain health is a growing field; you can learn more about brain health and diet from the National Institute of Neurological Disorders and Stroke.

Researchers will continue to investigate the long-term effects of various fasting protocols and individual responses to better personalize dietary recommendations.