So what useful things for cycling does knowing your body fat or bone mass do? It just seems like one of the many gee-whiz numbers we like to boast.

Few people are going to have a body fat low enough to worry about materially adjusting their nutrition. And for your bones, diet and resistance exercise to keep those bones strong is needed regardless of whether they are currently losing strength or not.

So I'll do a Dexa scan when I get into my seventies and the doctor wants to determine if bone loss is happening. Till then I just do the normal things that keep them strong. I just get the body composition from my scale whenever I need a chuckle.