Obesity appears to play a protective role in heart disease

May 18 2009

Being overweight or obese is a leading contributor to cardiovascular disease (CVD) and associated risk factors; however, in patients with established CVD, obesity appears to play a protective role.

In fact, data suggest obese patients with heart disease do better and tend to live longer than leaner patients with the same severity of disease, according to a review article published in the May 26, 2009, issue of the Journal of the American College of Cardiology.

"Obese patients with heart disease respond well to treatment and have paradoxically better outcomes and survival than thinner patients," said Carl Lavie, M.D., F.A.C.C., medical director of Cardiac Rehabilitation and Prevention, Ochsner Medical Center, New Orleans, LA and lead author of the article. "Although these patients have a more favorable short- and long-term prognosis, we don't yet understand the mechanisms for why this might be the case."

The obesity paradox in patients with CVD, which was first noticed earlier this decade, is complex. It is likely due to a combination of obesity's impact on fat cells and other metabolic processes (e.g., insulin resistance, glucose metabolism, metabolic syndrome), as well as other consequences of being obese. Dr. Lavie speculates that excess weight may be somewhat protective because these patients have more reserves to fight disease than thinner patients. Another explanation might be that obese patients present with problems earlier due to physical deconditioning (being out of shape) and other non-cardiovascular symptoms and, therefore, have the opportunity to be diagnosed with milder disease.

Although obese patients appear to experience fewer cardiovascular events and have better survival rates, Dr. Lavie is quick to caution that patients with heart disease shouldn't incorrectly assume that gaining weight is the answer.

"Obesity is often what's causing high blood pressure, blockages in arteries, and increased risk of sudden death in the first place. Such excess weight has adverse effects on all of the major cardiovascular risk factors and has increased the prevalence of heart disease," he said. "Taken together, most studies are supportive of purposeful weight loss for preventing and treating cardiovascular disease."

Health-promoting behaviors to stay active and lose weight can also confer benefits beyond initial heart disease. For example, patients who are overweight or obese are at heightened risk of diabetes, which can further complicate treatment and outcomes. Patients who make sustained lifestyle changes, including regular exercise and some weight reduction through a reduction in calories, cut their risk of developing diabetes by roughly 60 percent.

"Obesity is skyrocketing in America and if this continues, we may see an unfortunate reversal to what has been a steady increase in life expectancy," says Dr. Lavie. "We need more research: first to prevent obesity in the first place; second, to intervene early enough so that patients who are overweight or obese won't develop heart disease; and then to better understand why these patients have a better prognosis once they have heart disease. Perhaps this information could lead to benefits for all patients, including patients with heart disease who aren't overweight or obese."

According to authors, obesity may soon overtake tobacco use as the leading cause of preventable death in the United States if current trends continue. Nearly 7 out of 10 adults are classified as overweight or obese. In adults, overweight is defined as a body mass index (BMI) 25 to 29.9 kg/m2 and obesity as BMI =30 kg/m2. Other indices that have been used less commonly, but possibly with more predictive power include body fatness, waist circumference (WC), waist-to-hip ratio (WHR), and weight-to-height ratio.

"Clinicians should emphasize to patients the importance of achieving and maintaining a healthy weight, as well as benefits that can be obtained from restricting their intake of calories and getting regular exercise of 30 to 40 minutes on most, if not all, days," said Dr. Lavie.