You have enough on storage to go for hours, days even weeks (depending on the energy demands).
For what it’s worth, during the earlier podcast episodes it was stated that you certainly got enough on board to go through one to two hours.
Anyway, some anecdotal evidence which perhaps explains why I asked the question I have asked:
(1) During my last Ironman I easily went through 7,500 kcal. During the swim I obviously didn’t eat at all. During the bike about 300 kcal per hour and during the run about 150 kcal per hour. The deficit easily amounted to 5,000 kcal. .
(2) When I train early I don’t have the option to prefuel my rides. So I get on the bike without having eaten for 10ish hours. Yet I am still able to get 2 to 3 hour rides in (eg Polar Bear +1). The more intense stuff (Z4+) I support with a gel or two. Though that’s only 100kcal a piece. Easy 1,500 kcal deficit right there.
(3) When I go skying with the nephews those little powerhouses hardly eat all day. You literally have to force them to sit down and eat something for lunch. Yet they are far from bonking.
Though all that doesn’t mean that fuel won’t help. Quite the opposite actually, it lowers perceived effort and generally makes things easier. However, it is still not a necessity to dose yourself in sugar on the bike. Especially not for various health reasons. For instance sake it’s super bad for your teeth and also to some extent for your organism. At least if you want to believe certain studies that indicate that sugar could play a role in cancerous diseases. I am no scientist to evaluate whether that’s sound or not. Ultimately, it doesn’t matter much. The dental aspect is already a showstopper for me.