If you want to lose weight, counting calories may be helpful. Calories are the energy in food. Your body has a constant demand for energy and uses the calories from food to keep you functioning. Here are some strategies that could work: skipping one or two high-calorie items that you might have otherwise eaten is a good place to start when cutting calories; choose lower calorie foods; and reduce your portion sizes.
Another importance is that this is used in people with systemic diseases that needs to maintain their weight. They are given total calories that needs to be followed daily to prevent weight gain as well as complications from their existing conditions.