A Misconception

Rather than being a tuber that has been upholstered, the phrase "Couch Potato" refers to an extremely lazy person.

The Origins of the Couch Potato

This state of affairs developed with the advent of remote controls for television. No longer required to get off the couch to change channels on the television, the lazy person could stay seated all day deriving hours of entertainment without having to change position.

Due to the laziness inherent in the couch occupier, they would rarely cook nutritious meals, surviving instead on junkfood often consisting of crisps¹ and sweets as well as the highly nutritious take-away meals². This diet and exercise regime resulted in the couch occupier becoming progressively rounder and potato shaped and, due to lack of movement, accused of having "put down roots". Hence the term Couch Potato.