What is the relationship between body composition and metabolic rate?

The correct choice highlights that higher lean mass generally increases metabolic rate, which is an important concept in understanding body composition. Lean tissue, such as muscle, is metabolically active and requires more energy to maintain compared to fat tissue. This means that individuals with a higher percentage of lean muscle mass tend to have a higher resting metabolic rate (RMR), allowing them to burn more calories even when at rest.

This relationship emphasizes the role of exercise and strength training, which can promote muscle growth and subsequently lead to an increase in overall metabolism.

The other choices do not accurately capture the dynamics of body composition and metabolic rate. While it's true that increased body fat can influence metabolism, stating that it simply decreases metabolic rate overlooks the nuanced interactions within the body. The assertion that body composition has no effect on metabolic rate contradicts established research that shows a clear link between muscle mass and metabolic activity. Lastly, attributing metabolic rate changes solely to age ignores the significant impact that changes in body composition can have over time. Thus, the focus on lean mass and its positive influence on metabolic rate is well-supported by scientific understanding.