Originally Posted by
RFHOLLAND
The question as stated has to do with a body moving at constant speed (zero acceleration).
No, reread the OP. It just refers to the road being flat, it doesn't say anything about constant speed. In most places, riding along a road for any significant distance will require slowing, stopping and acceleration for stoplights, traffic, pedestrians, whatever. Even if there are no such interruptions, every ride starts with an acceleration. Why would you assume OP was asking about a hypothetical but impossible infinite ride?
The discussion above has mostly acknowledged that weight matters very little while running n the flat, but that acceleration is where it would make a difference. Most of the argument has been about how much that matters.