Life is like a box of chocolates. If you're fat, it doesn't last long.
I find your analogy to be rather offensive!
It's okay, fat people are all food addicts. They cannot help it, they can't control themselves.
You should try to sympathize more with people suffering from being overweight, so that you understand what they're going through before you make inane comments like that. Empathy is important because it helps us understand how others are feeling so we can respond appropriately to the situation.