Cellular respiration converts the energy of fuel molecules to a form of energy that a cell can use to perform work. in an average day, most adult humans need to consume about 2,000 calories to maintain their health. however, the exact amount of dietary calories a person needs depends upon many factors, including the person's age, physical activity, size, and health. foods that we consume vary greatly in their nutritional content and quality. a large hard-boiled egg, for example, has about 75 dietary calories and contains about 70% of our recommended daily intake of cholesterol. molecules that come from the food we eat provide energy for the amazing work that goes on inside of our cells. this energy, stored inside of our food, is a form of