Originally Posted by stonecrd

Actually I don't think this is true since the amount of work required to do 20mi in 1hr is greater than the effort to do 20mi in 2hrs, I don't believe it is linear. If you do the calculations you find that you need to maintain ~261 watts to do 20mph for one hour which translates to 897kcal for my body weight. On the other hand to do 10mph in 2hrs you only need to maintain 52 watts which translates into only 358 kcal. So even though you are doing the same distance and trading speed for time you actually do about 2.5x less work overall during the ride.

I have heard a couple of nutritional people say that the key for weigth loss is really just burning the maximum amount of calories. There is a increase in fat burning when doing anaerobic vs aerobic exercise but the tradeoff in calories burned means that you are really better off just focusing on burning the highest number of calories.