IDIOMS

beer muscles

(idiomatic, humorous) A protruding stomach, supposedly indicative of excessive consumption of beer.

Example: 1979, "Letters: Summing Up Summerfest and Planning Ahead," Milwaukee Journal, 14 Jul., p. 10 (retrieved 3 Jan. 2010):
  Many people, especially after a few beers, grow “beer muscles” and are ready to fight for any reason.
1999, Phil Mushnick, "In-Arena Shows Are Big Turnoff," New York Post, 18 June, p. 94:
  The show has become a come-on for drunks to flex their beer muscles.
2009, Andrew W. Lehren and Christine Hauser, "In New York City, Fewer Murders on Rainy Days ," New York Times, 3 July (retrieved 3 Jan. 2010):
  â€œEverybody's out partying, people start drinking, old beefs pop up, and people get their beer muscles out and start fighting.”
1939, American Flint, vol. 28, p. 41
  Grothers Gribble, Berger, Wolf, Shadwill and the writer are still nursing their “beer muscles.” I mean German goitres.
1982, "Brewing firms says small is better," Milwaukee Sentinel, 2 Sept. (retrieved 3 Jan. 2010):
  â€œYou can't find a better-tasting beer,” said Farmer Cheatle, a resident who was losing a battle to hold in a bulging belly he called “beer muscles”.
1990, John Harvey, The Legend of Captain Space, ISBN 9780002235563, p. 33:
  Nick made legs of his fingers and walked them on the baby's belly. . . . “[L]ook at those beer muscles!”