If Americans continue to pack on pounds, obesity will cost the U.S. about $344 billion in medical-related expenses by 2018, eating up about 21 percent of health care spending, according to the first analysis to estimate the future medical costs of excess weight.

These calculations are based on the projection that in 10 years, 43 percent of Americans adults may be obese, which is roughly 30 or more pounds over a healthy weight, if obesity continues to rise at the current rate. Extra weight increases the risk of diabetes, heart disease and many types of cancer.

This report comes as the country struggles to find ways to curb medical costs and Congress debates health care legislation.

"Obesity is going to be a leading driver in rising health care costs," said Kenneth Thorpe, chairman of the department of health policy and management at Emory University in Atlanta. Thorpe did this special analysis on obesity for America's Health Rankings, the 20th annual assessment of the nation's health on a state-by-state basis.

Using weight data, Census statistics and medical expenditure information, Thorpe found:

• An obese person will have an average of $8,315 in medical bills a year in 2018 compared with $5,855 for an adult at a healthy weight. That's a difference of $2,460.

• If the percentage of obese adults doesn't change but stays at the current rate of 34 percent, then excess weight will cost the nation about $198 billion by 2018.

• If the obesity rate continues to rise until 2018, then Colorado may be the only state with less than 30 percent of residents who are obese.

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