Watching television can negatively affect physical fitness levels by promoting a sedentary lifestyle, reducing opportunities for physical activity. Prolonged periods of sitting can lead to weight gain, decreased muscle strength, and poor cardiovascular health. Additionally, excessive screen time can lead to mindless snacking, contributing to poor dietary choices and increased caloric intake. To counteract these effects, it's important to set limits on screen time and incorporate regular exercise or physical activities, promoting a more balanced and healthier lifestyle.