When you are burning a ton of calories, it doesn’t matter if you eat quality food or not, you just need calories that your body can absorb quickly. I used to ride double centuries (200 mile bicycle ride) with my family when I was a kid, and every rest stop you grabbed a handful carbohydrate-rich foods - granola bars, cookies, muffins, maybe some fruit like a banana or apple, tootsie rolls, whatever. We also put a carbohydrate/electrolyte mix in our water bottles. All because your body needs to absorbs calories. I had one ride where I didn’t eat enough and “hit the wall”, i.e. my body went into ketosis and started burning fat, and it does feel like you hit a wall, all of the sudden you have zero energy and every peddle stroke feels like a struggle.