Although fasting-abstaining from food for several hours to days-is generally considered safe and potentially beneficial for long-term health, concerns persist about its acute effects on cognitive function. Given the importance of sustaining adequate levels of cognitive performance for professional and personal activities, this potential side effect warrants careful examination. Here, we synthesize evidence from experimental studies comparing cognitive performance between fasted and satiated healthy adults using standardized psychological tasks. Analyzing 222 effect sizes across 3,484 participants (median fasting duration = 12 hr), our hierarchical random-effects model revealed no meaningful difference between fasted and satiated participants (g = 0.02, 95% CrI [-0.05, 0.10]), with low between-study heterogeneity (τ = 0.17). Notably, we observed modest reductions in cognitive performance for longer fasting intervals and for younger (vs. older) participants during fasts. Differences across cognitive domains (e.g., attention and inhibitory control) did not reliably explain the heterogeneity in effect sizes. These findings suggest that cognitive performance remains remarkably stable during short-term fasting, supporting the feasibility of fasting practices while highlighting nuanced considerations for implementation in health interventions. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

• Royal Society of New Zealand
• University of Auckland