Cyclists at risk for bone loss

Thing is... How can us casual cyclists see any greater bone loss than your average joe commuter? Yes we cycle to our desired destinations, but everyone else sits still in a car/bus/tube/train/cab/UFO, and we all probably do as much walking once we get to our destinations?

Surely you will only see bone deterioration vs a normal person if you cycle more than you walk?

Or am I missing something..

You know I can't help but think of Wall-E when you mentioned that.