Since 11 Jan 07, I have walked every single day for at least 20 minutes. This is my absolute minimum: most days I ran, lifted, or both. But, if nothing else, I always walked. My main goal is weight loss: I have lost 80+ lbs, and I'd like to lose another 20 or so. I also want good muscle definition. I'm at a particularly busy time in my life, and I am re-evaluating my walking. Most days, the bare minimum of exercise (20-30 min) is all I have time for. Would I be better served by spending that time lifting?