Fatherhood messes with your brain ... According to a new study, first-time fathers experience brain volume loss. Researchers found that the more that new dads are engaged in parenting, the more their brains shrink. On average, men lose about 1% of their gray matter volume as they transition to parenthood. And while it's "only" a loss of 1%, the bottom line is there is a loss. And, most would agree it's better to have more brain cells than less, wouldn't we?