I too was on a low carb / high protein diet for a while. I'm not overweight, in fact I work out regularly and was taking protein supplements (over 160 grams/day). My worry with the low-carb diet has been that your brain needs to synthesize carbs to create glucose. If it doesn't get enough of them, it will create it from MUSCLE tissue! This is called GLUCONEOGENESIS.
This is my chief concern about low carbs. I spend too much time lifting heavy chunks of iron to only lose it to my brain which is hungry for glucose.