+1 on riding more. I'm in the same boat as you though I'm riding a touch more. Between last April and this April I have lost 90+ lbs and needless to say my climbing has improved a great deal. I'm not great at it by any means, but I keep getting better at it.

Someone early on suggested finding a group ride +1 to that as well. Groups will help you push yourself and you'll ride faster than you do by yourself (at least I do). Are you in clipless pedals? These help too, better power transfer etc.

Pile on the miles.I started out last year lucky to do 50 miles a week, now I'm closing in on 200+ a week with plans of more as the season goes on.

Best of luck from one recovering fatty to another...oh yeah, one thing that really helped me with my diet was using an online calorie counter.