CORRECTED - Why are US kids obese? Just look around them-study

(Corrects name to American Journal of Preventive Medicine from American Journal of Preventative Medicine.)

By Julie Steenhuysen

CHICAGO, Sept 25 (Reuters) - Tough choices tempt kids at every turn -- whether it is soda in school, junk food ads on TV or the fast-food chain around the corner -- and school policies limiting physical activity only make matters worse, U.S. researchers said on Tuesday.

This throng of temptations may explain why childhood obesity has reached epidemic proportions, they said.

The collection of studies, published in the American Journal of Preventive Medicine, together suggest environmental factors and policies conspire to challenge the health of children in America.

"We have in our schools and communities a perfect storm that will continue to feed the childhood obesity epidemic until we adopt policies that improve the health of our communities and our kids," Frank Chaloupka, an economics professor the University of Illinois at Chicago, said in a statement.

While too many calories and too little exercise explain how children become obese, the research looks at environmental factors that contribute to these behaviors, and suggests policy changes that could make healthy choices easier.

"The environment that they live in matters," said Lisa Powell of the University of Illinois at Chicago, who studied restaurant and food store options in the neighborhoods and food-related television advertising aimed at teens.

She said when people cannot get to supermarkets but instead must rely on the convenience stores that proliferate in many poor neighborhoods, families end up eating less healthy food.