Parenthood, for all of its blessings, can come with its own set of health problems, according to a one-of-a-kind study from the University of Pittsburgh.

It backs up what parents have been saying all along: that physical exercise goes out the window as soon as the baby comes.

As part of a 17-year Physical Activity Study, 525 parents of newborns and toddlers were tracked for two years, to find out what impact parenthood has on physical activity and exercise.

The results were less than glowing when it comes to the physical health of parents.

Women who exercised an average of four hours a week before pregnancy, gave up about 90 minutes after junior entered the picture. Men fared even worse. New fathers, who used to log about eight hours of physical activity per week, gave up four and a half hours.

But why does this happen, really? They found some common sense reasons, as well as some surprising ones. Lack of financial means; less free time due to more parental obligations were cited as main reasons. However, the American all-or-nothing approach to fitness was found to be a prominent factor as well.

Healthy exercise can happen anywhere. It doesn't have to be exactly 60 minutes in a fancy gym. Taking 30-minute walks as a couple, pushing the baby in a stroller can do the trick just as well. Doing physical activities together also has the additional benefit of reducing the common tug-of-war between parents about who's turn it is to get out of the house.

Keeping active after you have kids is essential, not just for your heart health and metabolism, but also for your mental health, which is something you'll definitely need in the years ahead.

The New York Times July 5, 2007