Mila Kunis couldn't contain herself after late-night talk-show host Jimmy Kimmel said, "My wife and I are pregnant."

"Oh," she said to him, "you're both having a baby? ... You're not pregnant! ... Are you crying alone in your car listening to a stupid Bette Midler song? No."

But, Jimmy, that doesn't mean you have nothing to do with the pregnancy (we know you're half the magic) or with how the fetus develops.

In fact, research reveals just how much Dad has to do with his offspring's health: One way is through epigenetic changes to gene function (whether genes are turned on or off) that are transferred to a fetus via sperm when it fertilizes an egg.

For example, if a soon-to-be-dad is obese - 74 percent of U.S. men are overweight or obese! - it causes epigenetic changes that set up his offspring for metabolic and reproductive problems.

And a new lab study found that obese mice daddies have altered microRNA (molecular strands that regulate gene expression) in their sperm that then show up in their newborn daughter's breast tissue, increasing the daughter's risk for breast cancer.

So, guys, if you're overweight, give yourself time to lose weight before you become a daddy.

Say "bye-bye" to sat and trans fats, added sugars and syrups, and any grain that isn't 100 percent whole.

Start a daily exercise program of 10,000 steps (or equivalent), and complete two to three strength-building workouts weekly. Then, when you make your magic, you'll help start your child on the path to a long and healthy life.