Which of the following factors can contribute to changes in body composition?

The correct answer highlights the multifaceted nature of body composition changes. Age and metabolic rate are significant contributors because as individuals grow older, their muscle mass typically declines and fat mass can increase, often due to hormonal changes and a decrease in physical activity levels. Metabolic rate, which can vary from person to person, influences how efficiently the body burns calories and can lead to either weight gain or weight loss depending on the individual's energy balance.

In contrast, focusing solely on diet, stress levels, or body type does not capture the complexity involved in body composition. While these factors do play a role, they often interact with age and metabolic rate rather than function in isolation, making it crucial to consider a combination of these elements for a comprehensive understanding of body composition changes.