Aging affects metabolic rate as it generally leads to a decline in muscle mass, which is crucial for maintaining a higher metabolic rate. As individuals age, their bodies may also experience hormonal changes, particularly in levels of testosterone and growth hormone, that can further impact metabolism. Additionally, older adults may engage in less physical activity, also contributing to reduced energy expenditure. This combination of factors can make weight management more challenging, emphasizing the importance of strength training and regular physical activity to counteract the effects of aging on metabolism.