Have you seen Ryan Hall? He went from 125 to 225. Guarantee if he never ran and you saw him at the gym, you would say it is frame and that he couldn't possibly lose 50 pounds even though he was almost 100 pounds lighter. Hasan and Koko have the same frame as Coburn or Simpson. They just choose to be 15 pounds lighter so they can be the best in the world for 5k. That is why I chose them. I believe they are both in the top 5 in the world. The further away you move from the best, the less chance of being super skinny. Did you see Ahmed run his 5k? How many guys on his team are as thin or as fast?