In my world, morals don't enter into this at all. Health is a purely practical issue.
There are a whole bunch of advantages to a healthy mate:
- lives longer and can thus be enjoyed for a longer time.
- can carry hirs own weight (no pun intended) in the practical parts of a relationship.
- is less sick/tired/depressed/whatever and requires less tending to.
- and the classic: stronger offspring.
Add to this that we have a pretty strong instinctive reaction to unhealthiness, something that probably ties back into a primal fear of disease, death and other infectious and harmful things.
I can't get worked up over it. But then again, maybe this is just my own elaborate excuse to keep my own extra kilos