Many foods hold awesome amounts of energy . what does a burning cheese curl have to do with energy? ask joe cifelli. he's a professor at st. joseph's university in philadelphia. he also teaches fourth graders about nutrition—the science of food and diet. the first lesson is setting cheese curls on fire. cheese curls burn because they contain energy. "food is energy," cifelli explains. fire consumes that energy when cifelli burns a cheese curl. when you eat food, you are putting energy into your body. you use energy in many different ways—running on the playground, walking the dog, and brushing your teeth. everything your body does requires energy, even breathing and thinking. energy is measured in units called calories. scientists figure out how many calories are in a food by burning it, much as cifelli does, but they use a device called a bomb calorimeter. that machine measures the heat given off by the burning food. people on diets often worry about the calories they eat and count calories like wannabe scientists. but calories aren't bad! in fact, most kids need between 1,600 and 2,500 calories per day to grow and be healthy. if you eat more calories than you burn off, your body stores that energy. "it's like gasoline," cifelli says. "if you don't burn it, your body will put it in a storage tank." your body turns unused calories into fat for storage. having too much fat and being overweight can cause health problems. but you can work to stay at a healthy weight by listening to your body; be active and don't eat unless you feel hungry. healthy eating, cifelli claims, is just a matter of understanding the energy that goes in and the energy that is burned off. "it's about making choices," he says. joe cifelli says people are surprised by how much energy is in food. a hershey kiss has 26 calories, cifelli says. that doesn't sound like much, but if a machine could turn all that energy into power, it could lift a car six feet off the ground! when you eat, your body uses most of that energy to digest your food and keep the trillions of cells in your body running smoothly. the question below is an incomplete sentence. choose the word that best completes the sentence. eating too much fat being overweight can lead to health problems. a) but b) and c) from d) for