The correct answer is metabolism. When a person is very active, their body requires more energy to fuel their physical activities. This increased energy demand is met through the process of metabolism, which is the set of chemical reactions that occur in cells to convert food into energy. A higher level of physical activity leads to a higher metabolic rate, which means that the body is able to burn calories at a faster rate. This can result in weight loss and increased calorie expenditure. Therefore, a very active person has a high metabolism.
