If you are in a relationship, you know very well how situation can change day by day. You have to go to different restaurants regularly on date, have some fast food & grow weight. A Dhanmondi girl experienced so when she was in a relationship. She grew a lot of weight which grabbed the attention of her boyfriend. So one day he told her that she should lose some weight by going to a gym. That made her so angry that she slapped him. So before saying your girlfriend fat indirectly, think properly what can be her reaction later.