Packing on the pounds? Yep, you’re a Dad.

I used to go to the gym. I used to run. Occasionally, I would swim. I used to ride my bike to work everyday. Heck, some Saturday mornings, my wife and I would even ride our bikes just for fun. In short, I used to be a lean, mean fighting machine (well, minus the mean and fighting parts). I used to be.

Now my daily exercise consists of nothing more brisk than the 10 minute walk up the hill to work. The time at the pool is spent watching The Girl as she goes through her lessons and my beloved Rocky Mountain gathers dust on the wall in the garage. It shows.

Sure, some of the spare tire is due to the fact that I’m forty and, as we age, so does our body. But in reality I am just not as physically active today as I was pre-kids.

Nice to see I am not alone in this. The New York Times recently wrote about how kids adversely affect parents physical condition. Seems when the wee ones come along, something has to give and that something is often our trips to the gym.

According to a recent study by the University of Pittsburgh, on average those of us with kids lose about three and a half hours of physical activity a week. And men are affected more than women.

Women, who exercised on average four hours before children, lost about 90 minutes a week once they became mothers. New fathers, who used to log just under eight hours of activity weekly, cut back a whopping four and a half hours.

So, sure we are busy. And heck, we even might have a little less disposable income to throw around on things like gym memberships. But what was really interesting is that, while these are legitimate reasons why we have cut back our exercise, there is another reason at play. According to the study:

Too many Americans have an all-or-nothing mentality toward fitness, said Dr. Harvey B. Simon, an associate professor at Harvard Medical School. If they can’t find a 45-minute window to bike, they don’t substitute by strapping on a BabyBjörn and taking a stroll.

And still many of us find our kids a convenient excuse not to exercise. They give us a bulletproof excuse. Who is going to argue with us that, with a couple of kids, we have no time?

Reluctant exercisers use parenthood as “an excuse to not do it at all,” said Dana Wood, a mother and the health and beauty director for Cookie, a parenting magazine.

Still, at this time of adjustment, we new Dads need to take time to keep up our fitness levels.

“Reducing their activity in this critical period of time is probably not going to help their adjustment in terms of a new person in their house,” Dr. Fulton (an epidemiologist in the division of nutrition and physical activity at the Centers for Disease Control) said. “The long-term stuff, the chronic-disease risk reduction, is great, but immediately, they’re not getting the mental-health benefit.”

Lately, I’ve realized how much I miss riding my bike. What had been a daily activity for 7 years has happened a handful of times in the past year. So, 2 weeks ago I started going for bike rides after the kids went to bed. The weather is cool and there is still enough daylight. It really is amazing how such a little thing like a 20 minute bike ride can completely clear your head and re-energize you.