Green’s Dictionary of Slang

(Aus.) to overeat.

1946		(con. 1912) B. Marshall George Brown’s Schooldays 23: Henson barging in his plate as well with a great gutzing glint in his eye.
1946		D. Stivens Courtship of Uncle Henry 111: Too much gutsin’ — eh? Too much gutsin’ — that it?
1984		Partridge DSUE (8th edn) 515/2: since ca. 1890.
1986		R.G. Barrett Godson 221: [T]hey [...] flopped around [...] gutsing themselves on Promite sandwiches.