Green’s Dictionary of Slang

(orig. US) carbohydrates, or a meal or food that contains a high percentage of carbohydrate.

1977		C. McFadden Serial 139: She knew she shouldn’t be munching out on carbos like this.
1992		R.G. Barrett Davo’s Little Something 8: I’m a footballer. I need the carbohydrates.’ ‘Carbo arseholes’.
1999		Guardian G2 9 Nov. 8: The no-carb regime lets you gorge yourself.
2001		N. Barlay Hooky Gear 96: He use survival tactics. Eat woodlice full of protein an carbs.