Cygirl...think about it this way:

If you are following a low carb plan, carbs are restricted, right? That leaves us fat and protein.
Now...let's say that you are following a maintainence program at around 2,000 calories per day. Your Carb level for maintaining is 60 grams of carb per day.
So....we have 60 grams of carb at roughly 4 calories per gram...240 calories.
You need some protein...let's estimate that you like meat and eat about 120 grams of protein per day (remember, this isn't the total weight of the meat; just the number of grams of protein that the meat contains since meat is also comprised of water and fat as well). Protein is also roughly 4 calories per gram...so you have another 480 calories there.
Between the carbs and the protein, you are at 720 calories of your total of 2,000. Guess where the balance of your calories is going to come from? Yup...fats. To get the balance of your calories, you'll need about 142 grams of fat at roughly 9 calories per gram which would equal about 64% of your total daily caloric intake. Even if you were to increase your protein intake to 150 grams per day (that's a lot of meat, BTW), that still leaves your total daily percentage of calories from fat at 58%.
By today's medical guidelines (AHA et al), 58-65% of your daily caloric intake from fat is dietary suicide and yet those on low carb plans find that their overall health and bloodwork improve dramatically.
I don't find the ratios of this Optimal diet plan to be that much of a stretch when I look at it from this perspective.