When becoming a dad for the first time, men often express a desire to adopt healthier habits. They pledge to eat more nutritiously, increase their exercise and drink less alcohol.
Men put on extra pounds — as measured by an increase in body mass index (BMI) — during the first few years of fatherhood, whether or not they live with their child, the study found.
Meanwhile, their peers who don’t become fathers actually lose weight.
The study, which was conducted by researchers at Northwestern University’s Feinberg School of Medicine, was published Tuesday in the American Journal of Men’s Health.
“Fatherhood can affect the health of young men, above the already known effect of marriage,” said Dr. Craig Garfield, the study’s lead author and a professor of pediatrics at Northwestern University, in a released statement. “The more weight the fathers gain and the higher their BMI, the greater risk they have for developing heart disease as well as diabetes and cancer.”
Two decades of data
For the study, Garfield and his colleagues analyzed data collected on more than 10,000 young men over a 20-year period as part of the National Longitudinal Study of Adolescent Health. The men had their BMI measured at four different times during the study: early adolescence, later adolescence, mid-20s and early 30s. The data also recorded if and when the men became fathers — and whether they lived with their child (“resident” dads) or not (“non-resident” dads).
The analysis revealed that first-time resident dads experienced, on average, a 2.6 percent increase in their BMI during the period of the study, while non-resident dads experienced a 2 percent increase.
For 6-foot-tall men, that translates into an average of 4.4 pounds for the resident dads and 3.3 pounds for the non-resident ones.
By contrast, the men who did not become dads during the study lost an average of 1.4 pounds.
The researchers controlled for such factors as age, race, education, income, and marriage status — all of which are also known to affect BMI.
The BMI changes observed in the study may seem small, but “it is important to remember the study examines mean estimates of BMI on a population level and therefore may provide conservative estimates,” Garfield and his colleagues write in their paper.
“Nevertheless,” they add, “becoming a father increases the BMI trajectories of young men.”
Why it matters
The researchers speculate that the weight gain is the result of the men altering their pre-fatherhood eating and exercise habits.
“You have new responsibilities when you have your kids and may not have time to take care of yourself the way you once did in terms of exercise,” said Garfield. “Your family becomes the priority.”
New dads tend to have less time to work out at the gym or go for a run. And they may be snacking more — perhaps without realizing it.
“Anecdotal evidence does exist of fathers cleaning their children’s dinner plates,” write Garfield and his co-authors.
And why is this weight gain important? There are a couple of reasons.
“Adolescent and early adulthood BMI often sets a course for men from which it is hard to deviate” — a trajectory that can lead over time to an increased risk of heart disease, type 2 diabetes, cancer and early death, the researchers note.
But the study’s findings also have implications for children’s health, as other research has shown.
“In families with an overweight father and a normal weight mother, the odds of having an obese child 4 years later were 4.18 times greater compared with two normal weight parents, and, if the father was obese, the odds rose to 14.88 times greater,” explain Garfield and his co-authors. “Notably, having a normal weight father and an overweight/obese mother was not a significant predictor of child obesity.”
This study, like all studies, has its limitations. Some of the earliest BMIs in the study were self-reported, for example. Furthermore, the study looked only at men who became fathers by their early 30s. Data on older first-time fathers might reveal different results.
Still, the findings suggest that men need to pay more attention to their own health — and their health-related behaviors — as they transition into fatherhood.
Becoming a dad is “a magical moment where so many things change in a man’s life,” said Garfield. “Now the medical field needs to think about how we help these men of child-rearing age who often don’t come to the doctor’s office for themselves.”
You can read the study in full on the American Journal of Men’s Health website.