In a new study published in the American Journal of Men’s Health, researchers from Northwestern Medicine analyzed the body mass index (BMI) of over 10,000 men from their adolescence, and into their mid-30s. They compared nonfathers, resident fathers (who lived with their children), and nonresident fathers, and found that both dad groups showed an increase in their BMI between adolescence and fatherhood.
In fact, the average, 6-foot-tall father living with his child gained an average of 4.4 pounds after becoming a dad for the first time. Nonresident fathers gained 3.3 pounds on average.
Nonfathers, on the other hand, actually lost 1.4 pounds over the same period.
“Regardless of what kind of father you were, your weight actually increased,” said Dr. Craig F. Garfield, the study’s lead author. “So all fathers ended up increasing their weight as they go through fatherhood.”
Researchers took into account such factors as race, education, income, and screen time, as well as their marriage status, which previous research has shown affects a person’s weight. Though each participant experienced a weight increase over time due to age, the data showed that additional weight gains were contingent on fatherhood status, according to the study.
“For men who become fathers, their whole life changes,” said Garfield, who noted that they may be sleeping less, exercising less, and experiencing more stress — all factors that can lead to weight gain, he said.
Kermyt G. Anderson, a co-author of the book Fatherhood: Evolution and Human Paternal Behavior, indicated that the study may have been a little skewed, given its narrow age range, which doesn’t account for any changes individuals may make after early fatherhood.
However, he did admit that the research points to fatherhood as an isolated factor that contributes to weight gain, saying that “It’s common sense in a way.”