According to my Garmin watch, I have burned through 3,500 calories so far today which is almost a marathon…
I too have essentially browsed fridge and cupboards and I suspect I have consumed more than 3 500 calories:)
Regarding fuelling, I learnt this lesson when I was doing marathon training. For a half marathon, I don’t really need anything other than a cup of tea in the morning. But as soon as I run past 27 km I hit a wall and unless I’ve eaten something I will have a major problem. Today as I’d eaten breakfast, I brought a huel bar with me and a keto bar with me. I had them at 65km with a cup of tea. And this is one massive difference between running and cycling, if I’m running I have to eat on the move, cycling. I had a very dignified snack stop :) and then seemingly had no further problem getting back on the bike and within a few minutes back into the swing of things.