I started a fitness program at age 22 when, three months into my first job after graduating college, when I realized I was becoming sedentary. I started with a 1 hour exercise class three times a week. About 3 years later I added in a 45 minute weight training session three times a week on my lunch hour. A couple of years after that I replaced the exercise class with running because I didn't have time for it since I was going to night school for my master's and had a wife and two kids.

Five years later I added swimming. A couple of years after that I began biking on weekends and doing a spin class before work twice a week. Then, for a few years, I did a few triathlons. Then I had knee surgery (to repair the effects of 25 years of running), hung up my running shoes for good, and began biking to work. Now I realize that driving a car to a spin class is the definition of insanity.

The point is, over a period of 29 years, I slowly evolved a 3 hour per week exercise program into a 9 hour per week lifestyle, which includes swimming, weight lifting, biking to work, and biking for joy on the weekend.

I have never been sedentary, and never NOT been fit, so I don't have any concept of what that even feels like. All I can do is explain how I got where I am. When a sedentary person my age says "Oh, I want to be fit like you, I'm going to start exercising" (and I hear that often), my response is "Ooh... that's tough". And then they want to know what I mean by that. Here is what I say:

Starting an exercise program after years of a sedentary lifestyle is like giving up smoking after years of being a two pack a day smoker. It is not impossible - people do it all the time (see the example from dwr1961 above), but more people fail than succeed.

My "addiction" to exercise started much like a smoker's addiction to cigarettes. It started small, and grew over the years. The two pack-a-day smoker started with 2 or 3 cigarettes a day, and it grew from there. A few years go by and two packs is nothing to them, and quitting is nearly impossible. It's the same way with exercise.