>> I feel like this is greatly exaggerated. I did half of that in 3 days (500km) with the last day being 250km (because I was sick of doing it) and I didn't fee

>> I feel like this is greatly exaggerated. I did half of that in 3 days (500km) with the last day being 250km (because I was sick of doing it) and I didn't feel any such "caloric furnace" I think this depends on your fitness, especially your aerobic and anaerobic thresholds and the shape of your lactate curve. Less fit people burn a lot of glycogen even at lower wattages which results in crazy hunger when your glycogen stores are depleted. Trained people are able to burn mostly fat at relatively high wattages and even skinny people have a lot of energy stored in fat. Personal anecdote: I decided to use the pandemic to get back into shape. When I started accumulating endurance kilometers, I had to eat a carbo-gel every 30 km and I still felt really hungry after the ride and I had to devour enormous portion of pasta immediately. Now I can easily go 100 km on empty stomach and I do feel kind of hungry after that, but nothing exceptional.