@Edward
This issue has come up before at least a year ago, where a morbidly obese guest broke a bed that was not sufficient to the task if my memory serves me right the host's conjecture was that she should have been told in advance.
In the same post, a commenter alluded to a court case of morbidly obese man have a toilet collapse under him with obvious unfortunate consequences.
The beds that hotels use are of an industry standard designed for comfort, strength and longevity and carry a commensurably premium price.
I think good manners would suggest that a person with such a condition should bring this to the attention of the Host, as very few hosts would have installed a bed sufficient to the task. I think an additional problem certainly in America is, that people that are morbidly obese don’t see it as a problem and trying to convince them otherwise, would lead to a pretty bad review.
Additional there is the difference between mass and weight, a bed designed to take two people weighing in total 300Kg (circa 660ibs) is not necessarily designed to take the weight of one person weight 250kg.
Perhaps Fred could offer a solution to this problem?