Oh yeah. That makes sense. Its super counter-intuitive. Running a marathon gets harder as the miles stack up. Huge respect for anyone that can do an ironman. Fasting starts out very hard and gets trivially easy by day 5. The accepted explanation is your body just taps out on making the hormone that makes you feel hungry (ghrelin) after 3~ish days. You don't actually get hungrier and hungrier until you're in supraphysiological amounts of pain. The need to eat just kind of fades away - so you're just literally doing nothing. It feels like a non-achievement.