If you get down to 15/16 stone no reason why you can't learn in a 152. I'm 6 foot 2 inches and basically my weight varies from 15 0 to 15 stone 13lbs, depending on how lazy I feeling at the time.
I learnt in a 152 - admittedly, the school found a fairly thin instructor to teach me, but its possible. I just can't take another passenger my size with me, and I tend to fly on my tod when I rent the group 150, for safety sake - otherwise I fly 172s.