You don't just balloon in size like that without either a medical condition or some serious psychological problems. If my wife did gain an obscene amount of weight, chances are it would be due to other factors, and those factors would likely lead to relationship problems. Possibly even divorce but it's impossible to say for sure.
In other words, weight gain and divorce are both possible effects stemming from some other cause.
Getting older means you have a higher chance of gaining weight. As you get older you have to work harder to stay slim.
This being ATOT it doesn't surprise me how many say they would divorce over an issue such as weight gain. But in the real world many factors beyond normal control lead to weight gain. Stress of dealing with a d-bag spouse, aging, diet, having kids.
Now if the person did nothing to combat the weight it is one thing, and you should have a talk with them and make sure they understand that gaining weight is a health issue and you should be supportive of them in loosing the weight so they will be healthier.
But I'm sure the typical ATOT response would be . OMG you're so fat, LEAVE!!!
Of course then most ATOTers would wake up from their nightmare and go back to surfing the internet for their perfect woman.