Obesity and excess weight, and their negative impact on health, have become a significant focus for physicians and other health-care experts in recent years.

But new research at Washington University School of Medicine in St. Louis shows that an escalation in the number of those considered obese or overweight in the United States continues, signaling an ongoing upward swing in chronic health conditions as well.

The study is available online June 22 in JAMA Internal Medicine.

Compared with a similar study published in 1999 that estimated 63 percent of men and 55 percent of women age 25 and older were overweight or obese, the new data from 2007-2012 indicate that nearly 75 percent of men and 67 percent of women now are overweight or obese.

'This is a wakeup call to implement policies and practices designed to combat overweight and obesity,' said the study's first author, Lin Yang, Ph.D., a postdoctoral research associate in public health at the School of Medicine. 'An effort that spans multiple sectors must be made to stop or reverse this trend that is compromising and shortening the lives of many.'

Adult Americans who are obese now outnumber those who are considered overweight, according to the new findings, which estimate that 67.6 million Americans over the age of 25 are obese and an additional 65.2 million are overweight.

In the new study, Yang and Graham A. Colditz, M.D., DrPH, a disease-prevention expert and deputy director of the university's Institute for Public Health, estimated the prevalence of obesity and those who are considered overweight, by gender, age and race/ethnicity. The sample size included 15,208 men and women aged 25 and older, which is representative of more than 188 million people.

Colditz also was a co-author on the earlier 1999 study, which used survey data collected from 1988-1994.

Parsing the data in the new study, the researchers found that African-Americans have the highest rates of obesity, with 39 percent of black men and 57 percent of black women considered obese. The researchers also found that 17 percent of black women are extremely obese, meaning their body mass index is over 40, as are 7 percent of black men.

Among Mexican-Americans in the study, 38 percent of men and 43 percent of women are obese. For whites, 35 percent of men and 34 percent of women are obese.

The study points out that because clinical practice for the prevention and treatment of chronic conditions has focused on screening high-risk populations, people in higher-weight categories are more likely to be diagnosed with weight-associated diseases such as diabetes, heart disease, high blood pressure, osteoarthritis and some cancers.

The authors suggest that public health experts should focus efforts on risk-reducing strategies such as physical environment interventions, enhancing primary care efforts to prevent and treat obesity, and altering societal norms of behavior.

'Delivering these strategies is a priority to counter the burden of obesity on contemporary and future generations,' they noted.

Colditz, the Niess-Gain professor of surgery and associate director of prevention and control at Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine, focuses much of his research on disease prevention.

'There are many things we can do to interrupt this worrisome and costly trend, and the benefits go well beyond what's obvious to the eye,' Colditz said. 'Some cancers, for example, can be prevented by eating a healthy diet, exercising and keeping weight in check. We need to do what we can to change behaviors of current and future generations to reverse this preventable societal burden.'

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This work was funded by the Washington University School of Medicine Transdisciplinary Research on Energetics and Cancer Center, which is funded by the National Cancer Institute, National Institutes of Health (NIH) and Siteman Cancer Center, grant number U54 CA155496; The Foundation for Barnes-Jewish Hospital, and the Breast Cancer Research Foundation.

Yang L, Colditz GA. Prevalence of Overweight and Obesity in the United States, 2007-2012. JAMA Internal Medicine, published online June 22, 2015.