Physical activity may not be key to obesit...( We would love to say that physical ...)

"We would love to say that physical activity has a positive effect on weight control, but that does not appear to be the case," Cooper said.

The recent study included 149 women from two rural Nigerian villages and 172 African American women from the west side of Chicago and suburban Maywood.

Adjusted for body size, the Chicago women burned an average of 760 calories per day in physical activity, while the Nigerian women burned 800 calories. This difference was not statistically significant.

Diet is a more likely explanation than physical activity expenditure for why Chicago women weigh more than Nigerian women, Luke said. She noted the Nigerian diet is high in fiber and carbohydrates and low in fat and animal protein. By contrast, the Chicago diet is 40 percent to 45 percent fat and high in processed foods.

Results of the new study are similar to those of a 2007 study of men and women in Jamaica. Researchers from Loyola and other centers found there was no association between weight gain and calories burned during physical activity.

"Evidence is beginning to accumulate that dietary intake may be more important than energy expenditure level," Luke said. "Weight loss is not likely to happen without dietary restraint."

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