I know your gf will force feed you cake, but losing your own body weight is going to help a ton. I went from 152 to 140 (5'8") and my climbing, ability to hold a higher speed, sprinting markedly improved. Abs might start popping up too! Ha! The only downside: Everybody and their mom will say, "You got skinnier".

Oh, and climb hills, do intervals, and find people that are faster than you that will ride with you.