If you go off of ANY of those guesstimator websites to plan caloric intake based off of exercise output, you're gonna gain weight. I'm over 200lbs, and my BMR is ~82Kcal/hr. So on a 2-hour ride at my typical pace, I will burn ~165Kcal being a person, and ~1,300Kcal from moving the bike.

All three of my rides this week have been metric centuries over different routes, at different speeds. But roughly the same lengths.

63.0 miles / 1,572ft = 2,014kJ
63.1 miles / 2,994ft = 2,145kJ
64.7 miles / 2,000ft = 2,135kJ

Notice a pattern there?

I have done 4,000Kcal on rides before, though. Back in April I did 108 miles @ 19mph. 3,984Kcal.