Fasting Generally Doesn’t Impair Adults’ Thinking, Large Review Finds

A sweeping meta-analysis of 63 studies (3,484 participants) finds no meaningful difference in cognitive performance between fasted and fed healthy adults. Age matters (children fare worse when fasting); longer fasts may lessen performance gaps as ketones supply energy; testing later in the day and the presence of food cues can influence results; and the type of cognitive task matters. Overall, fasting appears compatible with maintained mental sharpness in adults, with caveats for kids and certain contexts, while metabolic benefits like autophagy and improved insulin sensitivity are noted but vary by individual.