Exercising is about more than just looking good. Just because you don’t appear to be overweight, you can still have more body fat compared to your muscle mass. Having a high body fat increases your risk for various diseases such as diabetes, heart disease, stroke, etc.
Heart disease risk can be reduced by exercising regularly. The main cause of heart disease is inactivity and eating foods high in fat and cholesterol. Exercise has a ton of benefits besides improving your overall health so just because someone doesn’t look overweight, doesn’t mean they should live a sedentary lifestyle.