Does Higher BMI Benefit Heart Disease Patients?
A person is said to be overweight when his or her BMI is between 25 to 29.9 kg/m2, and obese when the BMI exceeds 30 kg/m2. BMI, which stands for body mass index, is calculated by dividing the weight in kilos by the square of height in meters.
People who are overweight or obese are facing a higher risk of developing many chronic diseases including heart disease, high blood pressure, diabetes, sleep related to breathing disorders, joint disorders and certain types of cancer. Obesity has been marked as the most neglected public health problem and it has been a burning issue for nations worldwide.
Many studies have, however, shown that obese patients with heart disease have better outcomes than those who are non-obese. Many evidences suggested a survival benefit in overweight or moderately obese patients with chronic disease like heart disease. Such finding has been termed as ‘obesity paradox’, which has been reported, besides heart disease, for various disease groups including stroke, renal disease and diabetes.
In 2006, a paper published in ‘Lancet’ on August 19 by researchers from Mayo Clinic College of Medicine, Mayo Foundation in the United States showed that those patients with a low BMI had the highest risk for death while overweight patients had the lowest risk.
Researchers from St Luke’s-Roosevelt Hospital, New York reported in October 2007’s issue of ‘The American Journal of Medicine’ that the occurrence of death, heart attack, or stroke for hypertensive patients with heart artery disease was 30 percent lower in those who were overweight, obese and severely obese, as compared with those with a normal BMI. Hypertensive patients with the lowest BMI had the highest risk of death.
After reviewing 9 observational studies involving 28,209 participants with chronic heart failure, Canadian researchers reported in 2008 in the ‘American Heart Journal’ that overweight and obese patients, compared to patients with normal BMI, had reductions in cardiovascular death (decrease of 19 percent and 40 percent, respectively) and total death (decrease of 16 percent and 33 percent, respectively).
4 years later, researchers from UCLA (University of California, Los Angeles) published their findings online on April 12, 2012 in the ‘American Journal of Cardiology’ indicated that advanced heart failure patients (men and women) who were obese and had larger waist size were less likely to experience adverse outcomes.
During the 2-year follow-up, the researchers found that men with a high BMI and a high waist circumference were less likely to require a heart transplant or ventricular assist device placement and to have adverse outcomes like death. Similar outcome also applied to women who had a high BMI and high waist circumference.
According to researchers, men with a normal BMI and waist circumference were 34 percent more likely to experience adverse outcomes than men with a high BMI, and women with a normal BMI and waist circumference were 38 percent more likely to experience worse outcomes.
While there are several possible explanations, scientists are still unsure why such paradox exists for heart failure patients.
It is possible that overweight heart failure patients might benefit from increased muscle mass, and metabolic reserves in the form of fatty tissue. Meanwhile, higher levels of serum lipoproteins linked to increased body fat might also play an anti-inflammatory role, neutralizing circulating toxins and inflammation-related proteins.
Though an increased BMI appears to be beneficial in those with heart disease, obesity is associated with an increased likelihood of developing diseases and sudden death for the general population. Obese patients have a higher risk of sudden cardiac death (SCD).
In the Framingham Heart Study, the annual rate of SCD in the obese was nearly 40 times higher than the non-obese group. The study also showed that for every 1kg/m2 increase in BMI, the risk of heart failure increased 5 percent in men and 7 percent in women.
Does obesity paradox really exist or it is probably just a complicated situation. Perhaps, more research should be carried out to investigate the physiology behind it.
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