When I want to get to single digit bodyfat levels, I do a variation of the ketogenic diet in which I eat low carb, high protein, and moderate to high fat for three days. The last meal of my third day is a carbohydrate meal based around complex carbohydrates, upwards of 100gms. This is a three day cycle.
On the fourth day, I resume my low carb, high fat, high protein, however this time my cycle lasts 4 days. Then on my last meal of my fourth day I eat a carbohydrate meal upwards of 100gms. I then repeat the cycle again. So it's 3 days, then one carb load meal, then four days then one carb meal, then three days, then so on and so on.
Following this plan with high intensity exercise 3x/week, with cardio only once every 3 days, I can literally go from a muscular but soft 12% Bodyfat, to a ripped 7-8% Bodyfat in 6 weeks or under. 2000 calories day minimum.
Diet consists of steak, ground beef, eggs, pork, whey protein, summer sausage, Flax oil, and chicken smothered in cream cheese and bacon. Lots of fat, lots of protein.
I've been tinkering with ketogenic diets for approx 3 years now, and I've perfected it - for myself anyway. I don't have to kill myself dieting for a long period of time. 6 weeks is the maximum amount of time I need to stay on this diet. Once I get to about 7-8% bodyfat, I slowly add carbohydrates to my diet. Works everytime.