EXACTLY.  I've seen a lot of cases on this sub--where people are honest about their sex drive and both parties agree that if the other gets fat, they're leaving.  In every single instance, it turned out well.  They seemed happy.  The standard narrative would have you believe it's "shallow" and those relationships will be horrible compared to "it doesn't matter what they look like" relationships.  People work their ass off to keep a job, why is it magically impossible to work one's ass off to keep your significant other?    The happy relationships are like the Geneva Convention--either both sides keep up what they agreed to, or the deal's off.