My brother is a couch potato who watches TV all day.
couch potato
idiomA person who spends a lot of time sitting or lying down, often watching television, eating snacks or drinking alcohol.
Origin
first recorded 20th c.From couch + potato; coined by Tom Iacino in 1976 as a pun on boob tuber (from boob tube (“television”) and tuber (“potato”)); trademarked by Robert Armstrong from 1976–91.
After losing his job, he became a couch potato and rarely left the house.
She had vowed to run marathons, yet by winter she had slipped into the habits of a couch potato, surrounded by empty snack bowls and half-finished series.