A new review published in Psychological Bulletin suggests that short-term fasting, periods of not eating for less than 24 hours, does not significantly affect adults’ ability to think clearly, focus, or remember information.
The analysis, which drew on more than 60 studies involving over 3,000 participants, found that most adults maintain normal cognitive performance during short fasting periods.
According to lead author David Moreau from the University of Auckland, the human brain appears well adapted to temporary gaps between meals.
However, children and teenagers were an exception. Their mental performance declined slightly when fasting, highlighting why breakfast remains important for younger people.
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Why the brain copes without food
When the body runs low on glycogen, its main source of stored sugar, it begins using fat as fuel.
This produces molecules called ketones, which the brain can efficiently use for energy.
Researchers say this metabolic flexibility likely evolved to help humans survive in times of food scarcity.
Still, adults may notice small dips in concentration later in the day, when fasting aligns with natural drops in circadian rhythm.
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Experts urge balance and context
Health experts say these findings may reassure people who practice intermittent fasting for health or weight reasons.
Dr. Mir Ali, a bariatric surgeon at MemorialCare in California, told Healthline that short-term fasting is unlikely to cause a problem with mental performance.
Yet others, such as Stanford psychiatrist Dr. Debra Safer, caution that longer fasting periods or preexisting health conditions were not covered by this research.
People considering fasting should start gradually, stay hydrated, and ensure balanced meals during eating windows.
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Sources: Healthline.com, and Psychological Bulletin.
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