If its provided for you and the company doesn't say you can't take it with you, then its not theft is it.
If, on the other hand, the company require you to pay for the item, or not take it with you, then it would be.
I'm lucky enough to work for one of the ones that says the food provided for your consumption is yours... you may eat it wherever you please. Whether or not it is edible at all is an entirely different story...