Thinking about how much food I'll need for the solstice ride, (sponsorship link). Most estimates say up to 500 an hour. So the maths is 16 multiplied by 500, equals 8000. It seems a bit high; I don't think I can eat that much.
Looking at the profile above - read left to right - the toughest parts are in the last third; although it's never particularly flat. I'll be on my own so no resting in someone else's slipstream. So maybe the high requirement is right.