I think it may depend on a number of things. Time in the relationship. Reason for weight gain. How much you care/love the individual. The type of relationship it is.Bump this question. I am curious too. And does it the status have some effect : girlfriend vs FWB vs mistress vs wife vs roommate
Personally, if it's someone I love, short answer, is no. The longer answer is no unless I felt they were unhealthy with it too. But again if it is in a loving relationship I would talk to my partner and try understand why they were gaining weight and encourage then to look at diet and exercise, if not a medical reason for it. If it was someone I lived with, then as I like cooking, I'd change either what was being cooked or the quantity dished out.