Well, when I went on South Beach a few years ago before discovering Mark's Daily Apple I got hit with Carb Flu like it was raining hammers. I am still surprised my family didn't bloody well kill me as grumpy and grumbly as I was.
I have gone low carb seven or eight times since then and that was the only time I went through Carb Flu. The only difference I can see is that all the other times I went extremely low carb and consumed almost no vegetables in the first week (this time I have extended that indefinitely). I live on beef, chicken, pork, seafood, eggs, and nuts for the most part with bits of cheese, onions, bell peppers, and/or mushrooms as an occasional garnish for the meat.
First day I literally went from drag-ass zombie boy to alert and energetic.
As for nuts, I'm with Mark on the Macadamias. I can replace a whole meal with a cup of those in a pinch. But dry roasted Cashews run a close second, depending on my mood (usually they end up in stir fry with onions, peppers, and skirt steak).
On the other hand, my wife has had completely different experiences, so don't necessarily take this as *do this* advice, but just as one possibility. I find going stupid-low carb works best for me (and secretly suspect that adding more carbs is what has knocked me off the wagon in the past).