The Calorie you see on a food package is actually a kilocalorie, or 1,000 calories. A Calorie (kcal) is the amount of energy needed to raise the temperature of 1 kilogram of water 1 degree Celsius. scientists place the food in question in a sealed container surrounded by water and heat it until the food is completely burned off. Scientists then record the rise in water temperature to determine the number of calories in the product. Now scientists use different method to count calories.