I'm not necessarily against doing it quickly, but I see that as orthogonal to the protein/carbohydrate mix in the diet. As I see it, Person A currently has an average calorie intake of C, burns C' calories a day and requires P grams of protein and F grams of fiber. I would contend that it if you construct a diet plan with D<C' calories, then you will receive more favorable results with a proper diet that covers protein and intakes proper amounts of fiber and carbs and micronutrients. For me, this is a very vegetable heavy diet with daily protein supplements (I prefer brown rice protein + orange juice, to which you may add active culture yogurt)