Nov. 17 (Bloomberg) -- Two decades of improved treatments haven’t made a dent in the threat of heart disease in the U.S. because too many adults are obese, according to researchers from the University of Texas.

As the nation’s average body mass index, a measure of excess weight, surged between 1988 and 2006, the number of people with healthy blood pressure and blood sugar levels -- important measures of cardiovascular risks -- declined, according to a study presented today at the American Heart Association conference in Orlando, Florida.

The number of people who are obese has more than doubled in the past 30 years to 72 million people, or 30 percent of U.S. adults, according to the U.S. Centers for Disease Control and Prevention. The obesity surge has undermined advances such as the introduction of cholesterol-lowering drugs called statins in the late 1980s and public health programs that the CDC says have cut smoking rates to 21 percent, from 37 percent in 1970.

“We are getting fat just as fast as we are improving other factors,” said lead study investigator Kami Banks, a cardiology research fellow at the University of Texas Southwestern Medical Center in Dallas, in an interview. “We as physicians have to address obesity like it’s a medical problem. We have to prescribe things to our patients that help them manage their weight.”

About 17 million adults in the U.S. suffer from heart disease that can lead to a heart attack, according to the American Heart Association. Heart disease is the leading cause of death in the U.S. for both men and women.

8,264 Patients

The researchers analyzed medical records of 8,264 men and women, 20 to 85 years old, from the National Health and Nutrition Examination Survey, part of a series of surveys by the CDC that combines interviews with physical examinations. The average body mass index rose to 28.8 in 2005 and 2006 from 26.5 in 1988 to 1994, a “significant change,” the researchers said.

Obesity is defined as having a body mass index greater than 30, which is equivalent to about 186 pounds for a person who is 5 feet, 6 inches tall. Being overweight is defined as having a reading of 25 to 30. The index represents weight in kilograms divided by height in meters squared.

Researchers also found that the proportion of people with healthy blood pressure declined to 43 percent from 48 percent, while those with optimal fasting blood sugar dropped to 58 percent from 67 percent. Those factors appear to have undermined the benefits from reduced smoking and increased numbers of people who have their levels of LDL, or “bad” cholesterol under control, researchers said.

‘No Change’

“What we expected was in 2005 and 2006 that things would be better,” Banks said. “In 20 years we’ve been telling everyone to eat better and to lose weight. We were hoping we would see a positive change. What we’ve found is there’s been no change at all.”

Today’s research was funded in part by the National Institutes of Health, a U.S. agency.

The risk that obesity poses for heart disease is also spreading to younger people, according to a separate study that found children today have a greater chance of developing heart disease later in life than those a generation ago.

The study by researchers from Cincinnati Children’s Hospital Medical Center in Cincinnati found that children’s body mass index and left ventricular mass index, a measure associated with future cardiovascular risk and death, were both “significantly higher” in 2008 than they were 20 years earlier.

Echocardiograms

Researchers looked at 350 children who underwent echocardiograms in the mid-1980s and compared the information with data for a matching group of children in 2008.

They found that the average body mass index in 2008 for the children was 19.9 compared with 18.1 in the mid-1980s. For those ages 2 to 19 years old, the index is calculated by plotting the body mass index value on CDC growth charts, which are age and gender specific, according to the U.S. agency.

Between the mid-1980s and 2008, the number of overweight and obese children tripled. About 32 percent of children and adolescents are now overweight or obese, according to the American Heart Association.

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To contact the reporter on this story: Nicole Ostrow in New York at nostrow1@bloomberg.net.

Last Updated: November 17, 2009 14:15 EST