From the 1971 song "Amos Moses", a phrase referring to a person that gorges on food. It literally means that one can eat the equivalent of their weight in food, and unless the person exercises vigorously, the chances are high that they're huge.
(There) lived a man named Doc Milsap and his pretty wife Hanna, (and) they raised up a son who could eat up his weight in groceries! Named him after a man of the cloth, Called him Amos Moses!" -Jerry Reed, "Amos Moses
by TurtleShroom August 7, 2011