Fatherhood can shrink men’s brains — and that may not be a bad thing
Oct 30, 2026, 1:55 PM
Science suggests fatherhood doesn’t just change a man’s routine. It can actually change his brain, his hormones, his priorities — and even his body.
Neuroscientist Dr. Darby Saxbe has been studying what happens to men when they become fathers. And some of her findings might surprise you.
Dr. Saxbe spoke with Steven Bartlett on his podcast “The Diary of a CEO.”
“When dads told us before birth that they felt more bonded to their unborn baby, when they wanted to take more time off after work, and when they told us three months after birth that they enjoyed their babies more, they felt more connected and bonded to them, and they were spending more time taking care of their babies, they had more profound brain shrinkage,” she said.
How fatherhood changes men’s brains, hormones and priorities
And while the idea of a shrinking brain might sound alarming, Saxbe said it isn’t necessarily bad news. Think of it as a brain upgrade, not a downgrade.
“It’s losing all the extra pathways, and you’re sort of building a superhighway for that specific social information,” Saxbe said.
The research shows the brain is adapting to help fathers become more attentive to their children’s needs.
And then there’s testosterone.
Research suggests hands-on fathers can experience a drop in this hormone. And she said lower testosterone doesn’t automatically mean less masculinity.
“You don’t want testosterone levels that totally crash,” Saxbe said. “My lab has also found that when testosterone is really low after a birth, men have higher postpartum depression symptoms. You don’t necessarily want testosterone levels that are sky-high either because that can cause problems in your intimate relationship and it can make it hard for you to switch into nurturing and parenting mode.”
And those demands can be very different when you’re responsible for a tiny human who thinks 2 a.m. is ideal for playtime.
But fatherhood can bring a deeper change, too. Saxbe described how men can rethink what success really means — shifting from chasing the biggest salary to wanting more time with their children.
“A lot of men, if you survey parents, you say, ‘What are the most meaningful priorities in your life?’ Men are just as likely as women to say, ‘My kids,'” she said.
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The appeal of the dad bod
And what about the dad bod? Could that little extra padding actually be attractive?
“Part of it is if you show women torsos of different kinds of male body types, the dad bod is one women say, ‘He is more likely to be a hands-on father. He’s probably going to be more attentive. He’s going to be more caring.’ And those are things that are really attractive to women,” Saxbe said.
And if there’s one message for men preparing to become dads, it’s this.
“Great fathers are made, not born,” Saxbe said. “You might feel like you don’t have the qualities to become an amazing dad, but it’s really about your time, your investment, the practice that you get, and the extent that you care. That is going to shape you. It’s going to build a brain, and it’s going to build a body that will make you a tuned-in parent.”
So, fatherhood is a whole-body, whole-life transformation.
It’s the love, time, and care he brings to his children.
Read more of Katrina Guischard’s stories here.
