While fasting is recognized for its weight loss benefits, there are concerns that it might negatively affect cognitive abilities. However, a recent comprehensive review challenges this notion, suggesting that cognitive decline is not an inevitable outcome of fasting.
This extensive review analyzed 63 scientific articles, encompassing 71 independent studies with a total of 3,484 participants. The findings showed no significant difference in cognitive performance between those who fasted and those who maintained regular eating patterns.
This review effectively counters the prevalent belief that short-term dietary restrictions diminish mental capacities in healthy individuals, an idea perpetuated by popular culture—from snack advertisements claiming “you’re not you when you’re hungry” to the belief that breakfast is the most crucial meal.
The researchers, psychologist Christoph Bamberg from Paris Lodron University in Austria and cognitive neuroscientist David Moreau from the University of Auckland in New Zealand, aim to reassure individuals considering fasting that it will not compromise their mental faculties.
“For most healthy adults, the findings offer reassurance,” Moreau explained in a commentary for The Conversation. “You can explore intermittent fasting or other fasting protocols without worrying that your mental sharpness will vanish.”
In examining the data, the researchers employed Bayesian statistics, which provides a probability distribution instead of a simple yes-or-no answer. This method was used to assess whether fasting impacts cognitive function, drawing from multiple statistical sources.
The studies evaluated various cognitive skills, including memory recall, decision-making, and response speed and accuracy. As a whole, these assessments revealed that short-term fasting, with an average duration of 12 hours, did not significantly alter cognitive performance.
However, some nuances were observed.
The analysis identified slight cognitive performance declines during fasting periods extending beyond 12 hours, and more pronounced declines among children and teenagers, although they comprised a small portion of the participants.
This suggests that prolonged fasting may be more challenging for younger, developing brains, emphasizing the importance of three regular meals a day for children and teens.
Interestingly, cognitive tasks related to food were where the impact of fasting was most evident. This indicates that specific brain circuits might be more affected during fasting, although further research is needed.
“Performance deficits were often evident only in tasks involving food-related stimuli, such as looking at pictures of food or processing food-related words,” Moreau said. “In contrast, performance on tasks using neutral content was largely unaffected.”
He also noted that hunger might selectively divert cognitive resources or cause distraction only in food-relevant contexts, while overall cognitive functioning remains stable.
The researchers further observed that cognitive test performance in fasting individuals declined when tests were conducted later in the day, suggesting fasting might amplify natural dips in concentration related to circadian rhythms.
Beyond weight management, fasting has been linked to other health benefits in scientific studies, such as improved cardiovascular health and reduced inflammation levels.
Scientists believe fasting induces significant changes in the body’s operations, such as shifting from glycogen-based energy stores to utilizing body fat, specifically in the form of ketone bodies.
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Considering these factors, Moreau concludes that fasting should be regarded as a personal tool rather than a universal solution. It is best practiced with guidance from a medical professional.
“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,” Moreau said.
The research was published in Psychological Bulletin.
