Green’s Dictionary of Slang

(US campus) to ingest carbohydrates; spec. to drink beer.

1982		Star Trib. (Minneapolis, MN) 26 Sept. 1K/1: I definitely do carbo-load, but I don’t use the depletion phase,’ he said referring to the initial low-carbohydrate diet.
2002		Boston Phoenix 12 Sept. 🌐 The Boston Marathon [...] also provides an excuse to carbo-load beer and nachos while watching from the comfort of a Comm Ave bar.
2002		velogear.com 🌐 Sierra Nevada Brewery’s ales and lagers are the unofficial drink of many a peloton. Whether you’re a roadie or a denizen of the dirt, wearing this bright Pearl Izumi jersey lets you pay due homage to one of the tastiest ways to carbo load.