COUCH POTATO

A couch potato is someone who spends too much time sitting on the couch, watching TV, and eating junk food, such as potato chips and popcorn.

How do you think this idiom came to be? Is it because potato chips are a common junk food? Is it because when you are idle and eat too much unhealthy food, you start looking like a round potato? Or is there another reason?

                                                 image courtesy of dreamstime.com