Funny about bike enthusiasts in that I have seen many guys who put in many hours a week and they are fat. I guess they are just recreational riders and don't compete in bike races. Never seen a person running under 21 minute charity 5K road race that is fat.
When I lived in a city the leanest guys were the ones running with a television on their shoulder at night.
Yeah- lots of recreational cyclists are not lean at all. No surprise because after a ride they go pig out 😁 That being said, a sub 21 min 5K runner is about equal to a sub 25 min 10 mile cyclist- and you will find at that level and above they are equally lean. There are lots of fat 5 K runners out there too.
I trained a few times in the early season last year with a world class pro cyclist from Denmark. He was on a very strict diet to get super lean- even though he was riding about 20 hours (300+ miles!) a week!