burning like matchsticks in the face of the darkness

Amen! You start now, you're sparing yourself a lifetime of limitations, if not actual pain or ill health. And your focus on how you feel and move is excellent. I think of BMI as a guideline. We Americans are so adept at excusing what is often lazy habit -- I think doctors use it to help steer people toward healthier habits. You tend to record that you feel better when you exercise -- which is a wonderful feedback loop. I keep trying to build in better habits and it's so hard -- I'm glad to see you trying to build them NOW, while you are yet young. I get frustrated at my limitations that stem from out-of-shapeness. I would have enjoyed our cross-country trips more if I had been in better shape.