My carbs are fairly low. I take 'em down for show prep. I cycle 'em though. I'm not gonna sit low for very long. I'll typically start off with my carbs around 200, with 300-400 on heavy days, and hold that for four weeks or so. Then, I'll drop 'em a bit until six weeks out. Then, at six weeks out, I'll go three low days (50g or less), one high day (200g-250g), two low days (50g or less), and one medium day (100g-150g). Of course my fats will be through the roof and I'm taking glycerol, glutamine, and tons of bcaa's to keep my energy up throughout my training.
What will this do for me in the long term? Not lots. However, in the short-term (14 weeks), it'll pull me down around 2% bodyfat! Ultimately, I'm not the biggest fan of a ketogenic diet. However, with that being said, it certainly does work! You just have to stimulate your metabolism via thermogenics/supps.
I hope that answers your question. Out of curiousity... Why do you ask?