I've gone to ultras. You really need to have a range for the elites vs. everyone else. It's a very inclusive sport and you have participants that are fairly overweight even. Based on what I recall from my college track days where I knew my teammates' body fat percentages (4% to about 10%) I'd estinate that most elite men are at the lower end of that. Also because most men have more muscle mass their metabolic resting rate is higher so that definitely could be part of the reason why women and men peak performance is so close in ultras. They are using 10 to 15% more calories per hour I'd estimate. Also on a hilly course they need to tote that extra mass up a lot of extra climbs.

I am surprised no one has mentioned Ann Trason that won 13 (iirc) Western States and used to win many ultras outright.