“ But don’t say that it is a valid life choice to be fat.”
Of the many many fat people in the world, few of them made a knowing choice to be fat. Fatness is a side-effect, often of a variety of life problems, and not the result of a conscious decision to end up in a particular body type.
You even stated in another comment that most Americans are fat. Surely the vast majority of them did not decide to look that way.