How fit is "fat but fit"?

As a lot of people try to tell me that even though Americans tip the scale pound for pound more than most nations that most of those topping the scales, are fat but fit. Just how fit IS “fat but fit”? Watching these Olympics the term “best athletes in the world” seem to come up often. But I don’t see any 340lb+ male Olympians in any events at all. I would think if people can be fat and fit they would want to go head to head at the Olympics to show you can be clinically over weight but still be fit. Bobsled, luge, skeleton etc, those are gravity events, one would think a 5ft 6in 263lb woman slider would have an advantage with more weight for gravity to work with. Or to be a 5ft 4in 280lb woman, or 6ft 1in 403lb male curler would be seen at the games, all you have to do is walk around with a broom. Most of the Olympians I see don’t look to be more than 160lb for the women and 225 max (if that much) for the men. “Fat but fit” certainly don’t seem to be fit enough even for curling; how fit is it, and it is “fat but fit” enough to do ANY sports (walking on ice with a broom curling you can’t get much more low impact than that)?