More likely it's like most runners he eats a fair few carbs, which is the last thing you want to be shoving down your throat if you want to be "buff".
I'm sure weight lifting forums would be laughing at the runners here suggestions too. They tend to think of us as crazy with our "toxic grain" high carb diets and obsession with endurance. I've seen a few guys get in muscular shape quickly and none of them starve to do it. They went paleo. High protein, full fat and low carb diet. They changed to that way of eating and stuck with it. That along with three/four one hour intensive weight workouts a week and they transformed from skinny with no definition to muscular all over. One lad also went from what must have been close to obese to well defined muscular too. None of them took any longer than three months to see dramatic changes.
If body shape is your concern. Then running isn't the exercise that is best to it. If your goal is a muscular toned body then you'll need to work a weights regime into your weekly life.
All well and good but could they run the length of themselves?