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Steve Calhoun prepares to bite into a double cheeseburger in Yakima, Wash. If more of the world catches up to the pace of overweight Americans, it could seriously hurt the ability of the planet to sustain itself. - 

We all know the story: Americans are overweight and that costs us a lot as a country, in health care spending... and other ways.
But a new study has discovered our "obesity epidemic" may be doing harm to other countries -- and in fact, the future of the planet.

It found that if other countries begin to be as overweight as Americans, that could soon be the equivalent of having an extra billion people on Earth.

Here to talk with us in today's Mid-day Extra is Phil Edwards of the London School of Hygiene and Tropical Medicine. He was one of the authors of the study

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