ITHACA, N.Y. — Obesity accounts for nearly 21% of U.S. health care costs, according to a study conducted by researchers at Cornell University. The study showed that an obese person incurs medical costs that are $2,741 higher (in 2005 dollars) than if they were not obese. On a nationwide basis, that translates into $190.2 billion per year, or 21% of national health expenditures.

Previous estimates had pegged the cost of obesity at $85.7 billion, or 9% of national health expenditures.

“Historically we’ve been underestimating the benefit of preventing and reducing obesity,” said John Cawley, Cornell professor of policy analysis and management and of economics, and lead author of the study. “Obesity raises the risk of cancer, stroke, heart attack and diabetes. For any type of surgery, there are complications with anesthesia, with healing (for the obese). … Obesity raises the costs of treating almost any medical condition. It adds up very quickly.”

The study, which was conducted with Chad Meyerhoefer of Lehigh University, estimates the effect of obesity on medical expenses by treating the heritable component of weight as a natural experiment. Previous research reported the difference between the medical expenses of heavier and lighter people, which is a misleading estimate of the causal effect because obese and non-obese individuals differ in so many ways.