The Science Behind the Mental Clarity Diet

Butter coffee, keto, intermittent fasting. Does eating to prevent brain fog actually work?

Andrew Zaleski


Illustration: Johanna Walderdorff

AtAt the end of 2015, Geoffrey Woo was preparing to embark on his first experiment with radical intermittent fasting: a 60-hour stint, from Sunday night to Wednesday morning.

“At first I thought, is this even possible?” says Woo, co-founder of a San Francisco-based company called HVMN, which sells nootropic supplements the company says can “keep your brain sharp for the long term.”

“But I saw some of my co-workers doing it successfully, saying they were more clear and more productive.”

Woo didn’t begin fasting only for the reasons science tentatively recommends: to live longer or to lose weight. He was just as thin several years ago as he is today at age 30. What he was gunning for was a cognitive hack. “The plan was longevity and the cognitive benefit,” he says. Woo wanted to clear the “brain fog,” as it’s colloquially called, and optimize his mental agility.

“The first two times I tried to fast it was terrible. It was hard,” he says. “By the third time, it felt pretty refreshing. I felt pretty clear.”

Woo now cuts out all food for 24 hours once or twice a week. Every three months, he goes 36 to 72…