inc.com Scientists Debunk a Myth About Fasting and Brainpower Kevin Haynes 3–4 minutes

Maybe breakfast isn’t the most important meal of the day after all.

For years, Silicon Valley biohackers and productivity gurus have preached that skipping your morning meal clears “brain fog” and unlocks peak executive function. Meanwhile, traditionalists advise against making high-stakes decisions on an empty stomach.

Now, a “massive” review of scientific studies exploring the link between intermittent fasting and cognitive performance has basically concluded, “Eh, no biggie either way.”

“For most healthy adults, the findings offer reassurance,” said researcher and neuroscientist David Moreau of the University of Auckland in New Zealand. “You can explore intermittent fasting or other fasting protocols without worrying that your mental sharpness will vanish.”

In other words, powering through a long, grueling deadline on nothing but black coffee won’t sharpen your brainpower—and feasting on three square meals a day won’t diminish your mental acuity.

Moreau and psychologist Christoph Bamberg of Paris Lodron University in Austria pored over 71 independent studies that assessed the decision-making skills, memory recall, and response speed and accuracy of nearly 3,500 participants. Short-term fasting, averaging 12 hours, didn’t significantly change their scores.

There was, however, a “modest” reduction in cognitive performance among adults who fasted for more than 12 hours and “noticeable declines” among the small percentage of children and teenagers who took part in the studies. Researchers say this suggests that young, developing brains benefit from steady nourishment throughout the day and slow down when deprived of food for an extended period.

There was one other interesting outlier: Cognitive function tended to drag when fasting participants engaged in tasks involving food-focused stimuli, such as looking at photos of meals.

“Hunger might selectively divert cognitive resources or cause distraction only in food-related contexts,” Moreau said, “but general cognitive functioning remains largely stable. In contrast, performance on tasks using neutral content was largely unaffected.”

He and Bamberg also found that study participants who were fasting often did worse on cognitive tests conducted late in the day, suggesting that hunger might amplify the usual drop-off in concentration associated with natural circadian rhythms.

The duo’s analysis reinforces the fact that intermittent fasting causes significant changes in the body, starting with the way it stops getting energy from glycogen and instead begins burning fat. The benefits include weight loss, improved cardiovascular health, and reduced inflammation levels.

But depriving yourself of food for 12 hours or so apparently doesn’t clear your head or, conversely, cause brain fog. The bottom line, according to Moreau: Fast or feast as you see fit.

“Fasting is best seen as a personal tool rather than a universal prescription,” he said.

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