The first week is evil after being off the bike for a while. I was around 200 pounds 2 years back and riding 60km a stretch with no effort. I got distracted, got up to about 225 pounds (light yes, but read on) and wow! I couldn't go 10km without wanting to die. So I just pushed and pushed and now 2 months later I'm almost back to where I was. It just takes a lot of determination. The improvement every day is a real inspiration to me.