The first step to losing weight by counting calories is to understand what a calorie is and how it applies to your weight. A calorie is a unit of measurement that measures the amount of energy contained in a food or beverage.
Your body uses caloric energy to perform everything from basic biological functions to typing on your keyboard or jogging around the block. We all have a certain caloric requirement needed to maintain our current weight; if you eat fewer -- or burn more -- calories than that, you will eventually lose weight. This is called a caloric deficit. A good rule of thumb is that a caloric deficit of 3,500 calories leads to a weight loss of approximately one pound.