[WXLCKNO]

At 250w average during a 5 hour ride I'm burning like 1000 calories per hour or something mething close. Glycogen reserves are 2000 calories from a quick Google search, so that's 3k calories I need to make up for or 600 per hour. I'm sure there's a bunch of stuff I'm missing but 400 definitely makes more sense than 200

[nradov]

What you're missing is fat metabolism. If you're metabolically healthy (which you must be if you can hold 250W for hours) then you can make up the difference by converting stored fat into glycogen.

[avs733]

what is also missing is the ability to process calories in.

900-1000 calories might mean that in is optimal - but think about eating a full meal from mcdonalds every hour while massively extering yourself.

Training your gut matters and I've never seen anything that suggests much beyond 400 calories per hour is possible during meaningful exertion.

[matsemann]

Yup, part of my long distance cycle training was somewhat getting "fat adapted".

[WXLCKNO]

Right! That was a big missing chunk :)