Short-Term Fasting Maintains Cognitive Function in Adults

Research published in the journal Psychological Bulletin reveals that short-term fasting does not negatively impact cognitive performance in healthy adults. The study, led by David Moreau, Ph.D., an associate professor of psychology at the University of Auckland, analyzed data from 71 studies involving a total of 3,484 participants. The findings suggest that practices like skipping breakfast or intermittent fasting are unlikely to impair mental acuity in the short term.

Fasting, which entails abstaining from food for several hours to days, has gained popularity for its potential health benefits, such as improved insulin sensitivity, cellular repair, and weight management. Despite its growing trend, many people hold the belief that going without food can lead to diminished cognitive abilities. Moreau emphasized the importance of examining these potential side effects, stating, “Given how important it is to sustain adequate levels of cognitive performance for professional and personal activities, the potential side effects warrant careful, systematic examination.”

The meta-analysis focused on cognitive abilities, including memory recall, decision-making, and response speed and accuracy. Most fasting periods studied were short-term, with a median duration of 12 hours. Moreau noted, “Our main finding was that there is generally no consistent evidence that short-term fasting impaired mental performance.” Participants who fasted performed similarly to those who had recently eaten, indicating that cognitive function remains stable even in the absence of food intake.

While the overall results were reassuring, the researchers did observe some nuances. Cognitive performance showed modest declines for fasting intervals exceeding 12 hours, and children, who comprised a small segment of the dataset, experienced greater performance deficits compared to adults. “We were certainly surprised in one sense, as our results contradict the widespread assumption that fasting inherently compromises thinking ability,” Moreau remarked.

One notable aspect of the study was the context-dependent effects of fasting. Moreau highlighted that performance deficits were often noticeable in tasks involving food-related stimuli, such as images of food or processing food-related words. Conversely, tasks involving neutral content remained largely unaffected. “Hunger might selectively divert cognitive resources or cause distraction only in food-relevant contexts, but general cognitive functioning remains largely stable,” he explained.

The researchers also pointed to age as a significant factor influencing cognitive performance during fasting. Moreau stated, “Age was a powerful and salient moderator.” Children exhibited noticeable declines while fasting, supporting earlier studies that emphasized the cognitive advantages of breakfast in younger populations. This suggests that pediatric groups may require special consideration when evaluating fasting interventions, as their developing brains may be more vulnerable to energy deprivation.

The implications of these findings extend beyond academic research, carrying important messages for public health and fasting practices. Moreau concluded, “The primary takeaway is a message of reassurance: Cognitive performance remains stable during short-term fasting, suggesting that most healthy adults need not worry about temporary fasting affecting their mental sharpness or ability to perform daily tasks.”

Physiologically, fasting prompts significant metabolic shifts. As glycogen stores decrease, the body begins to utilize ketone bodies produced from fat tissue as an alternative energy source. Emerging evidence indicates that relying on ketones may confer various health benefits, regulate hormonal systems, and activate cellular repair processes associated with longevity.

Researchers argue that these findings support the viability of intermittent fasting as a health intervention for adults while highlighting the need to tailor fasting practices to specific populations, such as children or those with medical conditions.

For further reading, refer to the study: David Moreau, et al. Acute Effects of Fasting on Cognitive Performance: A Systematic Review and Meta-Analysis, Psychological Bulletin (2025). DOI: 10.1037/bul0000492.