It kinda is as a general rule to be honest. Not so much the single day ones, but the ones that go over 2 or 3 can lead people into pushing themselves way too far past their limits.
As for what I'd carry on something like this, it's as much about calorie density as anything. Real food is great (eventually you have to have something as your body will stop letting you eat crap), but you'll generally carry a ton of gels, nuts, sweets etc.
I would normally make stuff out of here, but I flat out wont have time this week before I go:
https://feedzonecookbook.com/portables/
I wont carry enough calories for 24 hours, but I almost certainly will carry enough caffeine to kill a horse. I'll put away dangerous amounts of it, but when your body is running hot like that, you can deal with more than you'd think. I'll have it in the form of drink tablets, actual tablets, and chocolate coated coffee beans.
I reckon maybe 14 hours worth of food (which weighs a LOT), and hope that I can get to the shops in time. For water, I'll literally be pulling it from rivers whenever I run dry (probably every 3 to 4 hours).