Oh, If you have put the weight on since you last rode a bike, there could actually be a learning or i should say re-learning curve of your bodies physical strength, coordination, balance,
weight distribution etc. it was just a though to keep in mind, because it made me think of my son's difficulty wakeboarding after a huge growth spurt between seasons, took him awhile to work out how to use his new body even though he's been wakeboarding since he was little.
Hope that helps......