"I told them, 'Look, by the time it gets in the pen to get weighed, it loses a lot of weight', " Mr. Gaede says.

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That's because obesity leads to so many different diseases--diabetes, heart disease, arthritis, mental disease--that it's hard to separate out the reasons for the reduction in costs once the employee loses weight.

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"As she loses weight and becomes more fit, she is burning fewer calories doing the same thing, so it is critical to change things up, " Jampolis said.

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