I would assume that a longer intestine would be better at absorbing nutrition from your food. So this explanation is actually the opposite of what I would expe

I would assume that a longer intestine would be better at absorbing nutrition from your food. So this explanation is actually the opposite of what I would expect. It really seems like they've switched cause and effect around, they eat a less energy dense/harder to absorb diet, and their intestines get longer to compensate, also they don't buff up as much, because they have to work harder for their nutrition.