I don't want to be the noisy newbie who just spouts questions (I try to give as much good info as I ask for

My question is about training when the goal is simply to increase total physical fitness and bodily efficiency.

I've never had weight problems, in fact atm I'm the heaviest I've ever been at 120 and 5'4" (I'm 19), and this after having sat at a computer all day at work and eating fast food. (shame)

However, my lack of fitness is more than evident when I try to run up stairs or take long walks with my fit hubby. He tires me out without trying.

Are there any special considerations I should make for a fast metabolism and low physical fitness?

I'm rather proud to say that after biking the small amount I already have, my digestive system is working better (take that, IBS!) and I have more energy during the day. =)

Your stories have been so inspirational, I don't want to quit! =)