Your body relies on what you eat and drink to maintain healthy tissues and to generate the energy used by cells. That energy is in the form of ATP (adenosine triphosphate), a molecule that contains high energy bonds. When those bonds are chemically broken, they release energy needed for cellular functions, such as muscle contraction. Not all foods can generate the same amount of energy in our bodies. We measure the energy value of food in calories.
Food contains different kinds of nutrients, which are substances that help maintain the body. There are six categories of nutrients: carbohydrates, fats, proteins, vitamins, minerals and water.