It's not super low carb, the carb amount varies depending on your activity level, I can have potatoes and butternut squash, a little fruit, but not grains or legumes. I can also have butter, olive oil and coconut oil. The theory is that we have not really evolved enough to digest grains. I was a bit skeptical, I am still not sure I buy it, but it does work, I feel pretty good, my pants are looser. Protein is moderately high, not that much more than a normal diet. I usually have sausage, veggies and an egg for breakfast, a hearty salad for lunch, and meat and two vegetables for dinner plus a little potatoes or butternut squash. I am eating at least five servings of vegetables, so it feels pretty healthy. No sugar, that was been hard at first, but once you are off sugar, the cravings stop. I was pre diabetic on my last blood test, so being able to get my blood sugar under control was major for me. Regular diets just left me hungry and cranky, or aggravated my other issues, so it feels good to be able to feel better and loose a little weight.
I have tried the typical high fiber, low fat diet, it just doesn't work. I would have a low sugar granola, fruit and low fat milk, but by 10:30 I was hungry and grabbing the first junky thing I could find. Now, I have bacon, veggies and an egg and I can last until noon, and still be able to eat with control, I don't get the sugar highs and lows because I am eating enough protein and fat, and not a lot of carbs. At first it is hard to believe you will not gain weight eating that much fat, but you don't.
The book I got has different versions of the diet based on your health issues, I am following the fibromyalgia version.