Not much more to say after this. Everything in life should be done in moderation, even cycling. As the others have pointed out, being active in multiple sports and physical outlets is paramount to health if you aren't concerned about being the best (in which case, stay at 140lbs and cycle all day, everyday ). The truth is, most of us cycle for sport and for health, but it should be supplemented by various other ways to ensure that our bodies stay healthy in every aspect.

As for gym alternatives, (not that I advocate paying the stupid exorbitant fee for participating) try crossfit type workouts. Olympic style: deadlifts, pullups, squats, bench, power cleans, clean&press and power snatches should be plenty for a well rounded athlete. I can honestly say that I'd rather be the athlete I am now (which can bench,squat and deadlift 315lbs, cycle a century and run a half mary-- not tooting my own horn, just making an example) than be someone who is just overtly great at one single thing. Besides, looking like a frail homeless guy on a $5000 bike is somewhat odd.