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When it comes to the battle of the brains, ladies rule.

Female brains, on average, act nearly four years younger than their chronological age while men’s brains act more than two years older, said a study of 84 men and 121 women.

The brain needs sugar as fuel. How it metabolizes glucose indicates a great deal about its metabolic age.

“It’s not that men’s brains age faster,” said Manu Goyal, assistant professor of radiology at Washington University School of Medicine, St. Louis. “They start adulthood about three years older than women, and that persists throughout life.”

One theory is that hormones could be shaping brain metabolism at a younger age, putting females on a more youthful pattern than males, who develop later.

Scientists hope to learn whether brain metabolic differences could play a protective role for women. “It could mean that the reason women don’t experience as much cognitive decline in later years is because their brains are effectively younger,” said Goyal.