The release sought by people who supposedly eat excessively as a substitute for sex, according to Freudian psychoanalyst Sandor Rado (1926). Probably a development of Freud's idea that "infant" sexual urges centred on body parts with a digestive function -- the mouth and anus -- and/or an effort to extend the master's theories about vaginal and clitoral orgasms. If you were overweight in a certain era, you might conceivably have heard from your analyst that you were neurotically using this sort of gratification as a stand-in for genital sex.
Now an almost extinct phrase, underused particularly by restaurant reviewers and writers of crank letters to sex columnists.