There is no excuse for ANYONE being overweight let alone a fat nasty tub of goo. If your S.O./Spouse/Mate is unwilling to eat responsibly enough to maintain a proper amount of weight that person is a piece of shit plain and simple. There is no other way to say it. Fat people have no legitimate excuses for their deplorable conditions.
There is something called a pre-nuptial agreement. One can be drawn up that would be compatible with love, honor, and obey. Love? Does the fat spouse love food more than you or your kids? Honor? By not being and looking his or her best, she/he is not honoring you or your family.
If wife or hubby will not abide by the terms of the marriage contact it is time for hubby or wifey to pay.