The waistlines of Americans continue to grow and a new study estimates that by 2015, 75 percent of adults will be overweight and 41 percent will be obese.

The percentage of adults in the U.S. that were obese increased from 13 percent in the 1960s to 32 percent in 2004, according to researchers at the Johns Hopkins Bloomberg School of Public Health's Center for Human Nutrition.

“The obesity rate in the United States has increased at an alarming rate over the past three decades,” said Dr. Youfa Wang, lead author of the study and an assistant professor at the Bloomberg School of Public Health’s Department of International Health, in a press release.

The proportion of overweight and obese Americans has increased at an average rate of 0.3 to 0.8 percentage points a year. Poorer Americans and some minority groups have been affected disproportionately, according to the analysis, which was published online in advance of the 2007 issue of the journal Epidemiologic Reviews.

Specifically, the study found that women ages 20 to 34, regardless of race or ethnicity, are becoming obese and overweight at a faster rate than men and children. It also found that 80 percent of black women age 40 and older are currently overweight, while 50 percent are obese.

“Obesity is a public health crisis,” Wang added. “If the rate of obesity and overweight continues at this pace, by 2015, 75 percent of adults and nearly 24 percent of U.S. children and adolescents will be overweight or obese.”

For the study, researchers analyzed 20 journal papers, reports and online data sets. They also used information from four national surveys to examine the disparities in obesity.

The findings included:

— Sixty-six percent of U.S. adults were overweight or obese in 2003-2004.

— Asians have a lower prevalence of obesity when compared to other ethnic groups. But Asians born in the U.S. are four times more likely to be obese than their foreign-born counterparts.

— Less-educated people have a higher prevalence of obesity than their counterparts, with the exception of black women.

— States in the Southeast have higher prevalence of obese and overweight adults than states on the West Coast, the Midwest and the Northeast.

— Sixteen percent of children and adolescents are overweight and 34 percent were at risk of becoming overweight in 2003-2004.

— Fewer white children and adolescents are overweight and risk becoming overweight compared with their black and Mexican counterparts.

This article was reviewed by Dr. Manny Alvarez