You'd probably should ask Robb Wolf's podcast this question. But I pretty sure I know what they'll say. If you are depleting your glycogen doing HIT your body wants to replace that glycogen. The main sources will be from carbs or protein. I think you know your can make glucose from protein...but the process is slow and compared to carbs more expensive. If you have a really hard workout you might have a hypoglycemic crash try to replace that glycogen from meat. If it were me I'd have a couple 2 or 3 sweet potatoes right after a hard HIT.
Would I be putting a grain-feed cow on a fad diet if I took it out of the feedlot and put it on pasture eating the grass nature intended?