I've also had drop in sex drive with low carbs when eating high protein and smaller amounts of 'good' fats.
However, I've been on the anabolic diet and eating low carbs with high fat has actually shot my sex drive through the roof.
In the past Alpha Male with low carbs lower fat didn't even help.
You can check out the ad thread over here. I'm very surprised by the diet and I have to say low carb and low cal have always hurt my drive but now I'm getting lean and still have the fire.