Age affects metabolism and fitness as metabolic rates generally decline with increasing age due to changes in body composition, hormonal shifts, and reduced physical activity levels. As people age, they tend to lose muscle mass, which further lowers caloric expenditure. Consequently, older adults may find it more challenging to maintain or lose weight compared to younger individuals. Engaging in regular physical activity, particularly resistance training, can help mitigate these metabolic declines by preserving muscle mass and enhancing metabolic rate, promoting healthier aging, and improving overall fitness and functionality.