America has reached a milestone that does not bode well for the nation's overall health, a study has revealed: U.S. adults who are obese outnumber those considered just overweight.

An estimated 67.6 million Americans over the age of 25 were obese as of 2012 compared with 65.2 million who were overweight, researchers at the Washington University School of Medicine in St. Louis are reporting.

Overall, three-quarters of U.S. men and nearly as many women are overweight or obese, they say in their study published in the JAMA Internal Medicine.

The study was based on data collected from 2007 to 2012 for the National Health and Nutrition Examination Survey, conducted by the Centers for Disease Control and Prevention.

Study co-author Lin Yang calls the findings a wake-up call highlighting the need for policies that can reverse the trend toward excessive weight gain and obesity, calling them a burden on the American health care system and society at large.

"Overweight and obesity are associated with several chronic conditions, including hypertension, heart disease, type 2 diabetes, osteoarthritis and some cancers," she says. "A collaborative effort must be made across the board to stop this trend that is compromising and shortening the lives of many."

The study used data from the CDC-led survey, including information on people's weight and height, used to calculate body mass index, or BMI.

A normal BMI is considered anything in the range of 18.5 to 24.9. A figure of 25 to 29.9 is considered overweight; 30 and above classifies a person as obese.

The National Institutes of Health offer a Web tool for determining your BMI.

The researchers say the new data shows women were much more likely to be obese (37 percent) than overweight (30 percent), with two out of three women in the United States being above a normal, healthy weight.

For men, 35 percent were obese, slightly less than the 40 percent considered overweight, but the result is three-quarters of U.S. men carry an unhealthy amount of weight.

The study showed African Americans had the highest rates of obesity among both men at 39 percent, and women at 57 percent, the researchers say.

Both younger adults, ages 25 to 54, and older adults 55 and up, showed comparable rates of overweight and obesity, the researchers say.

The significant number of U.S. adults who are overweight comes as no surprise, says Yang, as the trend has been building for years.

 "We kind of know the obesity epidemic is getting really severe," she says.

Still, she adds, she was stunned by the actual number of American adults now considered obese.

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