Darby Saxbe: Testosterone Expert: The Truth About DAD BOD & Why Women Find Fathers More Attractive!

The host opens with several surprising findings: fathers' brains lose volume, parents with more children may show markers of a younger-looking brain age, and hands-on fathers often have lower testosterone. A separate study is said to find that single women most often prefer a “dad bod.” Darby Saxby explains that the brain-volume change is concentrated in networks involved in mentalizing—reading other people's feelings and intentions—and in visual processing used to interpret an infant's face. She frames the change as a shift in how the brain is organized, not as a simple loss of ability. These claims are introduced as research findings discussed in the interview; the segment does not provide enough detail to evaluate each study's methods or strength.

Saxby says mothers and fathers show changes in some of the same brain regions, but mothers also show changes in subcortical areas linked to reward, intuition, and hormones, while the reported changes in fathers are more concentrated in the cortex. She presents this as consistent with fathers' caregiving involvement varying across cultures and circumstances. In her account, fatherhood is a facultative adaptation: fathers can provide substantial care when the family context calls for it, even though the level of involvement differs. She stresses that this does not make fathers unimportant; some are primary or sole caregivers. The host asks whether “facultative” means optional, and Saxby clarifies that she means flexible across situations.

Saxby rejects the idea that reduced brain volume necessarily means impairment. She explains it as more efficient communication: some pathways are reduced while the brain becomes better organized for the demands of parenting. She compares this with editing a film down to a version that is easier to follow. The host wonders whether a smaller mentalizing network means less empathy; Saxby argues the opposite, saying it may reflect more efficient processing of social information. She also says the degree of hands-on care is associated with the extent of brain change in her lab's work. The interview's explanation is a proposed interpretation of observed changes, not proof that all parents experience the same effects.

The discussion then turns to testosterone. Saxby says hands-on fathers typically show about a 25% decline, citing longitudinal research in the Philippines that follows men over time. She describes testosterone as adaptive in different reproductive contexts: higher levels may support competition and mating before conception, while lower levels may accompany investment in nurturing after a baby arrives. She says fathers who spend more time caring for children show a sharper drop, and that levels can rebound as children grow. She also reports that expectant mothers' and fathers' testosterone levels can correlate during pregnancy. The discussion presents these as population-level patterns; it does not imply that every father's hormone level changes in the same way.