Obesity Paradox Stumps Cardiologists

Obese and overweight patients survive longer after a diagnosis of heart failure than do their lower-weight counterparts. But does that mean fat is protective?

Not necessarily, according to a new study by Anita Deswal, MD and colleagues published in the Journal of the American College of Cardiology. But it is one of several possibilities suggested in the study.

“Weight loss due to advanced heart failure may not completely explain the protective effect of higher body mass index in heart failure patients, Deswal and colleagues wrote in the Journal of the American College of Cardiology. Deswal is a cardiologist at the Michael E. DeBakey VA Medical Center in Houston, TX.

In her study, known as ARIC for Atherosclerosis Risk in Communities, Deswal found that in 1,487 patients ages 45 to 64 with incident heart failure, 35% were overweight and 47% were obese before their diagnosis. Over a 10-year follow-up period, 43% of the patients died. But the patients who had normal weights had a higher death rate—51%. In the group of overweight patients that rate was 45% and in the obese it was 38%.

The trend occurred regardless of smoking status, history of cancer, or diabetes.

The simplest explanation for the phenomenon is that the normal-weight patients were already sicker, because many heart failure patients have spontaneous weight loss. Or, it could be that heart failure was diagnosed at an earlier onset in patients who were overweight or obese, since physicians are looking for signs of it in heavier patients.

But Deswal said the picture is more complicated. Perhaps the overweight patients have a survival advantage because their fat stores war of cardiac cachexia.

A more complex hypothesis advanced in the article is that obesity “alters the natural history of heart failure through neurohumoral pathways” and that higher levels of serum lipoproteins may neutralize bacterial lipopolysaccharides, thus attenuating a detrimental cytokine response seen in heart failure. Or this adipose tissue may produce higher levels of soluble tumor necrosis factor receptors .

Another idea is that fat patients have more circulating stem cells, and decreased adiponectic levels and an attenuated renin-angiotensin system and catecholamine response. Both could mean improved heart failure survival.

The research does not answer the question of whether obese patients with heart failure should lose weight. "Only a randomized controlled trial of targeted weight reduction in obese patients with heart failure could help resolve that question, the authors wrote.