Explain how 28% of american or 80.2 million people aged six and older are physically inactive. why is it a problen

A high percentage of American people aged six and older are physically inactive because of the modern lifestyle which is mainly sedentary.

First of all, children spend a lot of hours sitting at school and when they go home they do exactly the same thing. They don't engage in physical exercise as even in their free time they choose to play games which don't require active movement, such as computer games.  

This is a problem because children who aren't involved in physical activity have more possibilities to become obese or develop other health problems, such as cardiovascular diseases, from a very young age. Also, people who face obesity problems at a young age are more likely to have them as adults as well.

So, establishing good habits about physical exercise at a young age is of critical importance.    

unrelated sentences to be eliminated?

where exactly is the sentence