What Is Energy?
Mechanical Engines
Cellular Engines
Similarly, we burn food in little engines in our cells called mitochondria.
Calories
Calories
The amount of energy a food can produce is measured in calories. When a person eats more food than the body needs, the body changes the extra calories into fat. Eating fewer calories than the body needs will cause a person to lose weight.The number of calories needed by people each day depends on how much energy their bodies use. For example, an athlete usually needs more calories than an adult who works at a desk all day.