A global review of 71 studies concludes that short-term fasting does not significantly impair cognitive function in adults, though children and adolescents might face challenges. The study provides reassurance for those practicing intermittent fasting and highlights considerations for vulnerable groups.
The health benefits of intermittent fasting are well-documented, but concerns about its impact on mental performance have left many wondering if skipping meals could leave them less sharp. A comprehensive review of 71 studies conducted worldwide seeks to resolve these uncertainties.
The findings, published in the journal Psychological Bulletin, provide strong reassurance for adults, indicating no substantial difference in cognitive function when going without food for periods ranging from eight to 24 hours.
“People often worry that if they fast they won’t be able to concentrate at work or study effectively,” senior author David Moreau, a neuroscientist at the University of Auckland, said in a news release. “Our results show that, for most adults, short-term fasting is unlikely to have a major impact on mental sharpness.”
However, the study reveals some important nuances.
In particular, children and adolescents tend to perform less well cognitively during fasting, underscoring the necessity of a proper breakfast before school.
Additionally, the timing of the fasting seems to matter. Participants who fasted experienced cognitive dips later in the day, which might amplify natural declines in circadian rhythm function.
Specific tasks, especially those involving food-related cues, also appeared to undermine performance in fasting individuals. Judging portion sizes or responding to food imagery, for instance, could be particularly distracting for those who are hungry.
“It seems the brain is quite resilient in the face of temporary food shortages,” added Moreau, who works in the University’s School of Psychology and leads the Brain Dynamics Lab.
“Humans evolved with periods of food scarcity, so it makes sense our cognitive systems can function well without constant refuelling,” he explained. “That said, children and teenagers appear more vulnerable, which fits with what we know about their high energy demands.”
The studies reviewed had a median fasting duration of 12 hours, with only a few extending beyond 24 hours.
“These results don’t mean fasting is risk-free for everyone,” Moreau added. “People with health conditions, children, and those fasting for extended periods may still experience negative effects. Our review highlights the need for careful consideration in these groups.”
The study’s lead author is Christoph Bamberg, who was a doctoral student at the University of Auckland and is now at Lodron University Salzburg.
Source: University of Auckland