That was United’s 11th defeat of the season, leaving them bottom of the East of Scotland Football League’s first division conference B, with four points from 13 games.
Athletic’s scorers were Kieran Jack twice, Jonny Grotlin and Rory Young.
Jordan Gracie’s United side now take a break from league duties, playing another East Lothian side, Ormiston, in the South Challenge Cup’s second round this Saturday.
Fellow conference B side Peebles Rovers are away to Preston Athletic in the same competition.
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Both games kick off at 2.30pm.