Short-term fasting did not impair cognitive performance in healthy adults, according to a systematic review and meta-analysis published in Psychological Bulletin.
Investigators analyzed 63 studies encompassing 3,484 participants and 222 effect sizes. Using a hierarchical Bayesian random-effects model, the pooled standardized mean difference between fasted and satiated participants was 0.02, indicating no meaningful difference in cognitive performance outcomes.
Fasting durations ranged from 3 to 336 hours, with a median of 12 hours. Despite variation in study design and task type, heterogeneity was low-to-moderate across studies. Subgroup analyses showed minor effects of fasting length, testing time, and age. Among studies with fasting durations under 48 hours, each additional hour of fasting slightly reduced the performance gap by 0.01 units. Cognitive testing conducted later in the day modestly favored satiated participants.
Cognitive domain analyses revealed negligible variation across attention, working memory, and executive function. Slight decrements were observed in tasks involving food-related stimuli, indicating that hunger may affect performance in food-relevant contexts. Younger participants performed worse when fasted, whereas adults showed stable cognitive outcomes regardless of fasting condition.
Across 71 study samples and multiple designs, the overall conclusion held, with minor design-specific nuances. The investigators concluded that cognitive performance remains largely stable during short-term fasting, supporting the feasibility of fasting and time-restricted eating practices without measurable cognitive detriment.
“Fasting now stands as one of the most popular contemporary eating regimens, with numerous health professionals endorsing it,” wrote Christoph Bamberg, MSc, of the Department of Psychology at Paris Lodron University Salzburg, and David Moreau, PhD, of the School of Psychology and Centre for Brain Research at the University of Auckland. “The rising prevalence of noncommunicable diseases associated with overeating further underscores the need to better understand the optimal frequency of food intake required to sustain daily performance, as well as the physiological and health effects of fasting.”
The study was funded by the Royal Society of New Zealand Marsden Fund and the University of Auckland. The authors reported no relevant financial conflicts of interest.
Source: Psychological Bulletin
