The word 'sporter' is not commonly used in English, therefore, there is no well-defined antonym for it. However, if we consider the root word 'sport,' then its opposite can be said to be inactivity or sedentary lifestyle. People with sedentary lifestyle or lack of physical activity are more prone to health problems such as obesity, diabetes, and heart diseases. On the other hand, people involved in sports or physical activities are usually healthier and mentally sharper. Therefore, it's essential to find the right balance and incorporate some form of physical activity in our daily lives.