In 2001, A. Mosterd and colleagues from the Netherlands studied the prognosis of patients diagnosed with heart failure. They did statistical analyses on more than 5,000 patients, some of whom had heart failure. They found that patients with low BMIs and low blood pressure had more in-hospital deaths than patients with higher BMIs. The researchers claimed that their discoveries supported similar findings from a 1993 study in Massachusetts, and since 2001, at least eight studies have supported the findings. So, even though obesity is a well-known risk factor for heart failure and would be expected to cause problems for obese heart-failure patients, it seems that the opposite could be true.
The obesity paradox extends to other conditions besides heart failure. Patients with chronic kidney disease most often undergo hemodialysis, where a machine filters impurities out of the blood, and dialysis. About 20 percent of dialysis patients die each year from cardiovascular complications. Studies by researchers at UCLA Medical Center have shown that dialysis patients with higher BMIs have a better chance of survival than those with lower BMIs [source: Kalantar-Zadeh].
To summarize, the obesity paradox goes something like this. Obesity is a major risk factor for cardiovascular disease (like hypertension, congestive heart failure, coronary artery disease) and chronic renal disease. However, in patients with these chronic diseases, it appears that obesity is associated with better survival. If this finding is actually true, it could have important implications for how physicians treat patients with chronic diseases. Doctors could conceivably stop putting patients on diets and recommending that they lose weight.
So, why does the obesity paradox happen? We'll find out on the next page.