A meta-review covering 63 articles, 71 independent studies and 3,484 participants found no meaningful cognitive gap between fasting adults and those eating normally.
Median fasting duration was 12 hours, and across memory, decision-making, response speed and accuracy, short-term fasting did not significantly change overall performance.
Longer fasts showed limits: intervals beyond 12 hours produced modest declines, while children and teenagers showed more noticeable drops, though they were a small share of participants.
Food-related tasks and later-in-the-day testing were the main settings where deficits appeared, suggesting hunger may selectively disrupt attention rather than broadly impair cognition.
The Psychological Bulletin review challenges common assumptions about fasting and mental sharpness, while the authors still frame fasting as a personal tool best tailored with medical guidance.
Can a practice with no immediate cognitive benefit, like fasting, still offer long-term neuroprotection for your brain?
Why does short-term fasting spare adult brains but significantly impair cognitive function in teenagers?