Essentially, yes. You do need to eat to keep your body functioning. Calories have to come from three places; carbs, proteins and fats (the macronutrients). When you restrict carbs you're left with the two alternatives, proteins and fats.

Protein is needed, protein is essential. It is the protein that is broken down into basic amino acids and used to build cells, repair cells, make enzymes, etc. etc. One gram of protein has 4 calories, just like carbs. Eating the bulk of your calories every day from protein would be a daunting task - meat is filling.

Fat, on the other hand, had 9 calories per gram - it is what we call calorie dense. It is also metabolically neutral. It will not cause a change in insulin or glucagon levels. Insulin, as we know is the fat storing hormone. Glucagon is it's opposite - the fat burning hormone. The two cannot work at the same time - for one to be present the other must not be. When we eat protein insulin and glucagon are realsed in equal quantities, when we eat carbs insulin is released, and when we eat fat neither are effected. This is why it is so difficult to lose fat on a high carb diet - you need glucagon and it cannot be present if you're constantly eating carbs and releasing insulin.

Therefore, getting the bulk of our energy from fat will not effect insulin levels, restricting carbs will keep insulin low, and eating our protein will keep our body happy and functioning. This combination is what allows us to burn fat, be healthy and not go hungry.

Getting the bulk of your calories from fats is also a lot easier than getting it anywhere else - because fat is so calorie dense. And let's face it - it tastes good

HTH
Nat