Cycling Is A Poor Form of Exercise :-(
I've gone to two local meetups with road cycling clubs. One was a social meet up, and the members seemed far more fit than the average person of their ages (most were older). At the second meet, everyone was ready for a ride in their gear. I was shocked by their appearance. In full lycra kit, they had comically oversized pot bellies, but with skinny noodly arms and legs.
Basically, cycling is just sitting. It is not weight bearing. Your bones become weaker as you sweat away minerals over long miles. Your muscles and bones don't become any stronger because they don't have to bear any weight. As a matter of fact, any additional weight is a liability, so additional muscle mass only penalizes you on climbs.
Even when I was riding many miles a week, I never lost any significant weight. In the past couple of weeks, I've been walking and hiking instead. I've lost more weight in these past couple of weeks than I did when I was riding upwards of 200 miles a week cycling!
Cycling for me is more about fun and recreation rather than "physical fitness." You become fit when you become stronger, and cycling may actually lead to the opposite.