Originally Posted by
OBoile
Indeed both of these are true. But, as you no doubt know, the effect is pretty small overall. The idea that calories burned should scale linearly with weight isn't close to being true (as you no doubt also know).
Absolutely as to weight--we're talking low double digit differences if that over the course of an hour.
The drag actually goes up much faster than linearly, however, so body size can make a much bigger difference depending on how it's distributed. It will not make much difference between 13 and 14 mph, but will account for a much larger difference in drag going from 19 to 20 mph, for example. Drag, obviously, translates much more directly into calories as it will need to be overcome on level surfaces as well as hills, unlike weight which is pretty much a non-factor on level due to inertia..