You shouldn't insult your friends.
John notices that his friend Bill is gaining a lot of weight lately.
John wants to tell Bill to lose weight.
John tells Bill that he's concerned about Bill's health and wants to see him lose weight and offers to help Bill in doing so.
John tells Bill that he has to stop eating like a pig and take care of his bloated body.
Bill is momentarily self conscious but is overall really happy to see his friend take an interest in his health and offer support.
Bill withers away in shame and embarrassment and begins to cry.