What impact does aging typically have on metabolism?

The correct answer highlights a common understanding of the physiological changes associated with aging, specifically regarding metabolism. As individuals age, there is generally a gradual decline in metabolic rate, which is often linked to a reduction in lean muscle mass. This decline in muscle mass is significant because muscles are metabolically active tissues that contribute to overall energy expenditure. As muscle mass decreases, so does the basal metabolic rate, leading to a lower overall calorie burn even at rest.

Additionally, aging is accompanied by changes in hormone levels, such as decreased testosterone and growth hormone, which also influence muscle synthesis and metabolic processes. The result is not just a decrease in metabolic rate but also a shift in body composition, often resulting in an increased proportion of body fat relative to lean mass.

In contrast, other options present scenarios that do not align with the established understanding of aging and metabolism. For instance, the idea of an increased metabolic rate and muscle mass is generally inconsistent with what is observed in older adults. Similarly, asserting that there are no significant changes in body composition fails to acknowledge the well-documented shifts that occur over time. Lastly, while appetite and nutrient absorption can vary with age, claiming an increase in appetite and nutrient absorption does not capture the comprehensive impact age has on metabolism and body