A hypocaloric diet, by definition, contains fewer calories than the body needs for daily energy requirements. Even if it's 100% protein, when it runs out (and it will, otherwise you're not hypocaloric), it needs to turn to body tissues (fat & muscle) for its needs. Some of the shortfall will be made up by burning fat, and some will be made up by striping amino acids from muscle to convert to glucose. Obviously, the "best" diet is the one that pushes the body to burn more fat and less muscle, but there's no way to get 100% fat loss, 0% muscle loss. The body doesn't work that way.
your looking at it totally wrong.
the body right now is using up energy. it comes from glycogen and fat.
to lose fat, consume less carbs and fat than what it will use.
when no food energy is available (carbs or fats) the body starts dipping into fat stores, and also starts to convert amino acids to glucose. the body converts amino cids to glucose very slowly, and also doesnt need very much at all, since when you are in an energy defecit, insulin levels are very low, and the body is then depending onfat for about 80% of its energy needs.
the prrotein you eat is barely knicked at all by glucoenogensis.