Does fatherhood make men fat?

You may have noticed that many new dads seem to put on few extra pounds after having kids for the first time. Now a new study from Northwestern University confirms the so-called "fatherhood effect," finding that men do indeed gain weight after they become fathers, regardless of whether or not they live with their children.

The researchers tracked the weight of more than 10,000 men from adolescence to young adulthood. The results showed that the typical 6-foot-tall man who lives with his child gained an average of 4.4 pounds after becoming a father for the first time. A man of the same stature not living with his child gained an average of 3.3 pounds.

On the other hand, the researchers found that men who were not fathers lost about 1.4 pounds over the same time period. The study was published today in the American Journal of Men's Health.

While a few extra pounds may not seem like much to worry about, experts say even a small amount of weight gain could have lasting consequences.

"We know that during this period of time -- late adolescence to early adulthood -- men's weight really has a long-term effect on their lifetime risk of developing diabetes, heart disease, cancers, and even premature death," CBS News medical contributor Dr. Holly Phillips told "CBS This Morning."

"Also there's the idea that it's easier to prevent weight gain in the first place than to lose weight, so we might be setting these men up on a trajectory for long-term weight gain."

The researchers took other factors into account that could affect weight, including age, race, education, income, daily activity, screen time and marital status, since previous research has established that marriage tends to result in weight gain for men.

"Fatherhood can affect the health of young men, above the already known effect of marriage," lead author Dr. Craig Garfield, associate professor of pediatrics and of medical social sciences at Northwestern University Feinberg School of Medicine, said in a statement.

Though the study just found an association between fatherhood and weight gain and did not look at cause and effect, several theories exist to explain the fatherhood effect.

"Some are very simple. With the new responsibilities of fatherhood you might not exercise as much," Phillips said. "Or there's what I call the 'human garbage disposal' phenomenon, where parents finish whatever's on their children's plates, so men are eating a lot more pizza crusts."

Phillips also explained that there could be more complex, neurobiological causes. "There are brain changes for both men and women around taking care of children in parts of the brain called the amygdala and that can affect our hunger reflex, as well," she said.

The researchers concluded that pediatricians could potentially play an important role in counseling fathers on their health, as many new dads do not have doctors of their own.

"New dads are coming into the health care system as a pediatric chaperone," Garfield said. "This is an opportunity to talk about things that are important for dad's health and the child's health and to offer dads nutritional counseling and mental health education."

And though not as commonly talked about, the latter may be just as important, as previous research by Garfield has found new dads are at an increased risk for depression in the first few years after their child's birth.

"We now realize the transition to fatherhood is an important developmental life stage for men's health," Garfield said. "It's a magical moment where so many things change in a man's life. Now the medical field needs to think about how can we help these men of child-rearing age who often don't come to the doctor's office for themselves."