Americans have reached a weighty milestone: Adults who are obese now outnumber those who are merely overweight, according to a new report in the journal JAMA Internal Medicine.

A tally by researchers from Washington University School of Medicine in St. Louis estimated that 67.6 million Americans over the age of 25 were obese as of 2012, and an additional 65.2 million were overweight. Their count was based on data collected between 2007 and 2012 as part of the National Health and Nutrition Examination Survey, an ongoing study conducted by the Centers for Disease Control and Prevention.

Stopping Americans' propensity to supersize meals and lead sedentary lifestyles has become a national priority in recent decades with the launch of efforts like Michelle Obama's "Let's Move!" program aimed at children, state-funded interventions that have nutritionists going door-to-door to educate people about proper eating habits, and the Food and Drug Administration's move last week to ban transfats from the food supply.

The NHANES data includes height and weight, which are used to calculate a person's body mass index. A BMI between 18.5 and 24.9 is considered normal. Someone with a BMI in the 25-to-29.9 range is considered overweight, and a BMI over 30 qualifies a person as obese.

Women were much more likely to be obese than overweight, with 37 percent of women in the former category and 30 percent in the latter. Altogether, two out every three women in the U.S. were above a normal weight.

The proportion of men who were obese was almost as high as women - 35 percent. But that figure was lower than the 40 percent of men who were in the overweight zone. With both groups combined, three out of four men in the U.S. exceeded a normal weight.

African-Americans had the highest rates of obesity among both men (39 percent) and women (57 percent). The researchers found that 17 percent of black women and 7 percent of black men were extremely obese, meaning their body mass index was over 40.

Among the group labeled Mexican-Americans, 38 percent of men and 43 percent of women were obese. For whites, 35 percent of men and 34 percent of women were obese. No data were reported for Asian-Americans, who until recently have been undersampled by NHANES.

Rates of the overweight and obese were comparable for younger (ages 25 to 54) and older (ages 55 and up) adults, according to the study.

Being overweight or obese increases the risk of a variety of chronic health conditions, including Type 2 diabetes and cardiovascular disease. Extra weight also can make people more vulnerable to certain types of cancer. The more you weigh, the greater the health risk, according to the National Heart, Lung and Blood Institute.