It appears that you know this answer already. Yet, if this man has this preoccupation with weight...whether he knows them or not...it is likely that if (when, if you become pregnant) you become overweight, he will do the same thing to you as he does (or says) about others.
It does not sound like a healthy relationship. His obsession (or whatever word is appropriate)is not likely to become better unless he sees it as something that he needs to change.
We do not change our behaviors ('good or bad') for anyone. We only change them for ourselves. There are too many cases of people who have tried and either ended up unsuccessful or bitter, because they chose not to change for themselves.