Age can affect an individual's metabolism due to natural physiological changes, including a decline in lean muscle mass and a decrease in basal metabolic rate (BMR). As individuals age, hormonal changes, particularly in thyroid hormones, can further slow metabolism, leading to weight gain if dietary habits remain unchanged. Activity levels may also decrease with age, compounding the effects of a slower metabolism. Therefore, incorporating strength training and staying active can help mitigate these effects by preserving muscle mass and maintaining a healthier weight, thus promoting longevity and overall health.