Ah, how I wish I could run, or even jog! But my ankles won't let me; I've messed them up so badly with all the abuse I gave them in my 20's that I feel fortunate to be able to even hike at all; even that will make them blow up if I overdo it. I spent about 4 months and $180 dollars in copays for physical therapy, with no real improvement. Now I can go for brisk walks with a little pain (icing and advil are my best friends

). I also work in whatever I can: swimming, elliptical trainers, yoga, anything that doesn't involve impact on my ankles.
Diamonda, I agree that to be really fit you need some intense workouts, but the fact is that for many people, parking on the far end of the parking lot and taking the stairs is a lot more activity than they've ever done. And not all of us want or need to be really fit. I got to goal on the first WW 123 program and never did more than walk--2-3 times a week for 20 minutes at work, and 2-3 times a week for an hour up and down hills in my neighborhood. The key was doing something every day.
Medical findings support this. I can't quote you one right now, but in general just getting out of your car and moving on foot is a lot more than most Americans do, and is enough to improve most people's cardiovascular health and increase their metabolism.
I'd hate to see someone get discouraged from their moderate exercise plan because they might think they could never do it "right"! As a 41 year old lawyer and former athlete, I've come to terms with the fact that I'm basically a sedentary person who works exercise in whenever I can. If that means a walk instead of a Pilates class, so be it.