When it comes to maintaining a healthy weight for a lifetime, the bottom line is -calories count! Weight management is all about balance—balancing the number of calories you consume with the number of calories your body uses or "burns off."
A calorie is defined as a unit of energy supplied by food. A calorie is a calorie regardless of its source. Whether you're eating carbohydrates, fats, sugars, or proteins, all of them contain calories. Caloric balance is like a scale. To remain in balance and maintain your body weight, the calories consumed (from foods) must be balanced by the calories used (in normal body functions, daily activities, and exercise).