The diet will provide all the nutrients that your body needs. Your energy will come from your body fat stores. There is no shortage of energy there. You will also be taking medication and vitamins that will improve your energy level. The 3 meals a day provide you with a steady source of energy without the blood sugar swings.
If you exercise you should keep your level of exertion sub maximal for the first week to give your body a chance to adjust to the change in macronutrients (Those nutrients normally required in the greatest amount; e.g., carbohydrates, protein, fats.) and the change occurring within the body from a principally sugar metabolism to fat metabolism for fuel.