Obesity causes prolonged inflammation of heart tissue that in turn boosts heart failure risk, according to a U.S. study of almost 7,000 people.

The latest findings from the Multiethnic Study of Atherosclerosis (MESA) are believed to provide the first large scale of evidence of such a link and give the estimated 72 million obese American adults another reason to change their lifestyle.

“The biological effects of obesity on the heart are profound. Even if obese people feel otherwise healthy, there are measurable and early chemical signs of damage to their heart, beyond the well-known implications for diabetes and high blood pressure,” senior study investigator Dr. Joao Lima, a professor of medicine and radiology at the Johns Hopkins University School of Medicine and its Heart Institute, said in a prepared statement.

There is “now even more reason for (obese people) to lose weight, increase their physical activity and improve their eating habits,” Lima said.

He and his colleagues tracked the development of heart failure in an ethnically diverse group of nearly 7,000 people, ages 45 to 84, who enrolled in the MESA study, starting in 2000. Of the 79 participants who’ve developed congestive heart failure so far, 35 (44 percent) were physically obese (body mass index of 30 or greater).

On average, obese participants were found to have higher blood levels of key immune system proteins involved in inflammation (interleukin 6, C-reactive protein, and fibrinogen) than non-obese participants. A near doubling of average interleukin 6 levels alone was associated with an 84 percent increased risk of heart failure.

“Our results showed that when the effects of other known disease risk factors — including race, age, sex, diabetes, high blood pressure, smoking, family history and blood cholesterol levels — were statistically removed from the analysis, inflammatory chemicals in the blood of obese participants stood out as key predictors of who got heart failure,” Lima said.

He added that doctors “need to monitor their obese patients for early signs of inflammation in the heart and to use this information in determining how aggressively to treat the condition.”

Lima and colleagues also found a link between inflammation and metabolic syndrome, which doubles a person’s chances of developing heart failure. Metabolic syndrome is a collection of risk factors — obesity, high blood pressure, elevated blood glucose levels, excess abdominal fat, and abnormal cholesterol levels — that increase the risk of heart disease and diabetes.

The study was published in the May 6 issue of the Journal of the American College of Cardiology. The MESA study was expected to continue tracking patients through 2012.

(Source: Johns Hopkins Medicine, news release, May 1, 2008)