Aging affects metabolism and fitness levels through a natural decline in muscle mass and hormonal changes. As we age, the basal metabolic rate often decreases, leading to weight gain if caloric intake remains unchanged. Additionally, older adults may face challenges with fitness due to reduced flexibility, strength, and endurance. These physiological changes can result in a more sedentary lifestyle, further exacerbating the decline in fitness. Regular exercise and strength training are essential for mitigating these effects, helping seniors maintain functional independence and overall well-being.