His hyperventilation has little to do with his weight. He has underdeveloped lungs.
Didn't we establish already some time ago that it is in fact a congenital cardiac valve condition that severly limits his stamina?
= It is not his lungs!
A heart condition wouldn’t leave him out of breath.
Wikipedia says this: “Masunoyama has been diagnosed with a congenital heart defect and also has lungs smaller than the average person. […]. He also has a portable oxygen tank he uses during practice when he is feeling out of breath.”
A heart condition on its own could most certainly leave him significantly short of breath. If he has decreased lung capacity <and obesity>-- what he has been capable in his career is pretty amazing. He demonstrates such Fighting Spirit during each bout. Impressive knowing how much this burst of energy costs him physically each and every time.