In paradox, obesity a factor in heart failure, but may limit effects
It’s a strange paradox: Obesity is one of the main contributing factors to heart failure but, once the problem develops, obesity mitigates its effects. “Heart failure may be one of the few health conditions where extra weight may prove to be protective,” said Dr. Tamara B. Horwich, a cardiologist at UCLA’s Geffen School of Medicine. New research by Horwich and her colleagues quantifies the magnitude of the benefit from being overweight and for the first time shows that the effects are comparable for men and women.
Heart failure occurs when the heart cannot pump enough blood to fully support the body. Symptoms include shortness of breath, fatigue, edema (accumulation of water in the limbs) leading to swollen feet and ankles, and cough. Causes include genetics, infections, cardiac disease and other problems, but they are all exacerbated by being overweight. An estimated 5.8 million Americans have heart failure, including more than 2.5 million women.
Horwich and her colleagues studied the records of 2,718 UCLA heart failure patients who had had their height and weight measured when they were first treated and 469 whose waist circumferences were measured. They then correlated the patients’ body mass index (BMI) and their survival, and also their waist circumference and their survival. BMI is a measure of body fat calculated from height and weight. A BMI over 25 is generally taken as a sign of being overweight, while a BMI of 30 more more indicates obesity. The team also assumed that a normal waist circumference was 40 inches for men and 37 inches for women.
The team considered adverse outcomes to include death, an urgent heart transplant and placement of a ventricular assist device to aid pumping. The researchers reported online this week in the American Journal of Cardiology that, two years after diagnosis, 63.2% of men with a BMI over 25 had survived event-free, compared with 53.5% of those with a normal BMI. For women, the comparable figures were 67.1% for a high BMI and 56.6% for a normal BMI. Considering only waist circumference, two-year event-free survival was 78.8% for men with higher waist size, compared with 63.1% for those with normal size. For women, survival in the two groups was comparable.
No one knows why obesity may help in relation to heart failure. Patients might benefit from increased muscle mass, as well as from metabolic reserves in the form of fatty tissue. In addition, increased levels of serum lipoproteins associated with body fat may have an anti-inflammatory effect. Alternatively, it may simply be that heart failure patients who are obese are diagnosed earlier, thereby giving them a greater chance of survival.
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