"You have to prove these schemes work otherwise it's just money down the drain," said Eleni Mantzari, who studies financial incentives in health at King's College London. People often revert to unhealthy habits once the financial motivation is gone, she said.
AP Medical Writer Maria Cheng in London contributed to this report.
Health incentives research: http://chibe.upenn.edu/
Marilynn Marchione can be followed at http://twitter.com/MMarchioneAP
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