ride bike lots, eat balanced meals with high quality protein; follow exercise routine; walk everywhere you're not biking to. lift weights.

one trick to muscle rebuilding is eating proteins one hour, max, after exercise. I'm not exercise physiologist, but there's some reuptake that occurs in a limited time frame after exercise.

I think just riding everywhere you go and eating lots of high quality food with proteins should help. dieting does not; i think i eat 4,000 calories a day sometimes. your metabolism sounds like its firing on high already.