Getting stuck on calories is not beneficial. Most current research shows that although calories are important, the more important part of weight is metabolism and digestion. So I'd say moderating intake of simple carbs is much more important than counting calories, especially since some high calorie foods won't make a person gain weight, such as fatty fish.
Low carb! meaning no simple carbs! google simple carbs and complex carbs!
You could try the Atkins diet. Before doing anything get the OK from your doctor.