Congratulations to Duncan for making this decision. He won’t regret it. Four years ago, my wife and I joined the local YMCA. At the time, I wasn’t obese, but I definitely had some flab around the midsection. My height (5′ 10″) and weight (195) at the time calculated to a BMI (28) that is getting near the obese category.
We did cardiovascular work for a few months and then started lifting weights. Our YMCA has equipment from TechnoGym that keeps track of your workouts. The cardiovascular exercises are done at a measured and constant heart rate, with the machine adjusting the intensity automatically to keep you in your zone.
I dropped down to almost 170 pounds. Then my weight started increasing again, even though I didn’t think that I really looked any fatter. The muscle that I was developing from lifting weights was increasing my weight.
If Duncan sticks with it — and I hope he does — he should forget about the BMI as his fitness improves. The most important factors are how you feel and the energy you have. I would also encourage finding a partner to help you with your motivation. My wife serves as my motivation. There are days when one or the other of us doesn’t really feel like going to the Y, but the other person makes them go. This is a Good Thing.