I don't doubt they're mostly telling the truth about themselves, but beyond that? It's more difficult to say.
> And I'm not really convinced that, in cycling, for example, it's realistic to have cyclists run through hundreds of kilometers of mountains day after day and still being as fresh as ever. But hey, believe what you want.
Ah, "it's tough, so it can't be true!". Those guys are the best at the world at what they do, and the ones they show on TV, are of course in the lead, so by default the ones in good shape. If you go see a bicycle race in person, you also get to see the ones lagging behind, some of whom are suffering a great deal. Truth be told, so are the ones in the lead, they're just going faster.
It's really hard to know exactly what's going on, but my whole point is that there are at least a few guys who compete clean. Saying they are all doping is extremely demeaning to those who do compete clean.