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• Posted November 5, 2025

Intermittent Fasting Doesn't Affect Mental Ability, Review Finds

Intermittent fasting shouldn’t dull an adult’s ability to think, remember and problem-solve, a new evidence review says.

Mental abilities like memory recall, decision making and responsiveness aren’t hampered by skipping a meal or fasting for a half-day, according to an analysis published Nov. 3 in the journal Psychological Bulletin.

“Our main finding was that there is generally no consistent evidence that short-term fasting impaired mental performance,” said senior researcher David Moreau, an associate professor of psychology at the University of Auckland in New Zealand.

“Individuals who fasted performed remarkably similarly to those who had recently eaten, suggesting cognitive function remains stable in the absence of food intake,” Moreau said in a news release.

For the evidence review, researchers analyzed data from 71 prior studies involving nearly 3,500 people.

“While fasting has become trendy over the years, there is widespread concern, often reflected in common sayings like, ‘You’re not you when you’re hungry,’ that going without food might acutely impair mental sharpness,” Moreau said.

Results showed no overall impact from fasts of 12 hours or less.

“We were certainly surprised in one sense, as our results contradict the widespread assumption that fasting inherently compromises thinking ability,” Moreau said.

“Across a broad range of diverse tasks, cognitive performance remained remarkably stable,” he continued. “Many people believe that missing a meal leads to immediate declines in mental acuity, but our synthesis of the evidence suggests otherwise.”

However, people’s cognitive performance did decline slightly if fasts lasted longer than 12 hours, researchers said.

Children also showed greater declines in brain power while fasting than adults, even in the short-term, researchers said.

“Age was a powerful and salient moderator,” Moreau said. “Children showed noticeable declines in performance while fasting, echoing earlier studies that highlighted the steady cognitive advantages of eating breakfast in younger age groups.”

The findings, Moreau added, suggest "pediatric populations may require particular consideration when evaluating fasting interventions, suggesting that the developing brain has a heightened vulnerability to energy unavailability.”

Overall, the results support the use of intermittent fasting, as people can skip meals without fear of a brain drain, researchers said.

“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.

More information

Johns Hopkins Medicine has more on intermittent fasting.

SOURCE: American Psychological Association, news release, Nov. 3, 2025