system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why is being sedentary so bad for your body?
gpt
Your body is sort of like a machine.  Regular use keeps the machine in good working order.  Your bones and muscles stay strong, your tendons and ligaments stay flexible.  So if you don’t exercise or have regular physical activity then you become weak.  Your body also more fuel in the form of calories the more it works.  So if you’re sedentary you run the risk of storing excess calories in the form of fat.  That fat and weight gain can cause significant health problems.  So it’s best to stay physically active.