New research contradicts the widespread assumption that skipping breakfast or another meal while fasting compromises thinking ability.
A new study, published by the American Psychological Association, has found that intermittent fasting, which involves not eating for several consecutive hours each day, often within an eight or ten-hour window, is unlikely to cloud most adults’ thinking in the short term.
David Moreau, associate professor of psychology at the University of Auckland and the study’s lead author, said: “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.”
Discussing the study findings, he said: “We were certainly surprised in one sense, as our results contradict the widespread assumption that fasting inherently compromises thinking ability.
“Across a broad range of diverse tasks, cognitive performance remained remarkably stable.
“Many people believe that missing a meal leads to immediate declines in mental acuity, but our synthesis of the evidence suggests otherwise.”
Researchers looked at 71 existing studies comparing cognitive performance in healthy adults who were either fasting or had recently eaten.
The studies looked at factors such as memory recall, decision-making, response speed and accuracy.
Published in the journal Psychological Bulletin, the data included 3,484 people.
The time spent fasting each day was across a range, with an average of 12 hours.
“Our main finding was that there is generally no consistent evidence that short-term fasting impaired mental performance,” Dr Moreau said.
“Individuals who fasted performed remarkably similarly to those who had recently eaten, suggesting cognitive function remains stable in the absence of food intake.”
He suggested fasting may also be beneficial for the human body, not just when it comes to losing weight.
“Physiologically, fasting triggers important metabolic shifts,” he said.
“When glycogen stores are depleted, the body uses ketone bodies produced from fat tissue as an alternative energy source.
“Emerging evidence suggests that relying on ketones may confer broad health benefits, modulate hormonal systems, and activate cellular repair processes linked to longevity.”
The researchers did say there was some evidence that brain performance may be affected after 12 hours of fasting, and there was an effect in children, who made up smaller numbers in the study.
“Children showed noticeable declines in performance while fasting, echoing earlier studies that highlighted the steady cognitive advantages of eating breakfast in younger age groups,” Dr Moreau said.
He said one intriguing finding was that poor performance in tasks often involved those related to food, such as looking at pictures of food or processing food-related words.
“Hunger might selectively divert cognitive resources or cause distraction only in food-relevant contexts, but general cognitive functioning remains largely stable,” he said.
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