Want vs Need

I was having a conversation the other day with a friend of mines reguarding weight loss. She said she wants to lose weight. I responded to her by saying you may want to lose weight but I need to lose weight. She asked "well its the same thing right ?" In context I guess you can say so but in this instance when talking about weight loss a want & a need are two different things to me.

In terms of weight loss for me a want is something you can do later like oh I want to pick up some bread but I can do it later because I have some at home. As opposed to a need & to me a need is oh I need to pay my rent because if I don't I will lose my apartment. So for me losing weight is a need I don't want to lose it to buy fancy clothes, I need to lose it so save my life more then anything.