Students discovered that the energy in food can be transformed into heat energy through burning and that the energy derived this way is measured in units called calories. Cheetos, which contain a lot of fat have far more energy than marshmallows, which are mostly sugar. Heat calories are 1/1000 the size of "food calories," the unit found on the back of food packaging. Calories are a measurement of energy; they are found incarbohydrates (and other foods), but calories are not equivalent to carbohydrates.