Why do people need food and water to live?

Answer 1

Food is necessary for survival because the food contains glucose, and glucose is the only source of energy for living organisms. No other thing can supply energy to living things, and glucose is available through food, so in order to get energy to survive, food must be eaten to obtain the necessary amounts of glucose.

Answer 2

Food supplies necessary nutrients and water supplies necessary hydration for the body's energy and fluid needs. The body constantly consumes nutrients, converting them to energy, even when the body is at rest. The body is made up of 70% fluids but these are also constantly being used and expelled as waste (such as during breathing). So both food and water must be continually consumed and replaced to maintain life. People can live longer without food than they can live without water.