Calorie deprivation - how bad is it really?

[Owlie]

LSD rides (long slow duration) use more fat because the Krebs cycle (where fat is burned) takes awhile. Faster rides at a higher heart rate use more carbs, generally. So, should overweight people do only LSD rides? No. It's the calories in vs calories out equation, for the most part.

Um...what Krebs cycle are we referring to here? The only one I'm familiar with is the one that burns everything (fats, carbs, amino acids) and is running all the time. Yes, going faster will preferentially burn sugars, because that's what is rapidly absorbed and doesn't need to go through extra enzymatic steps to be usable fuel.
[Biochemist slinks out of the room and goes back to her corner]