Both high body fat and high lean mass index independently predict better survival in patients with stable cardiovascular disease, according to a new report in the Journal of the American College of Cardiology.
The study provides yet more evidence for the "obesity paradox": while patients with a high body mass index (BMI) are at much greater risk for cardiovascular disease, overweight and obese patients with heart disease have a better prognosis than lean patients.
Dr Carl J Lavie, a professor at the Ochsner Clinical School of the University of Queensland School of Medicine in New Orleans and the first author of the new study, said it's possible that leaner patients may develop heart disease due to a genetic predisposition, while obese patients develop cardiovascular disease as a consequence of their excess weight. "It may not be if we made people fatter it would protect them, it may be that they got their heart disease for a different reason," he said.
How the research was done
Most studies showing an obesity paradox have relied on BMI, which is not always the best indicator of body fatness, Dr Lavie and his team note in their report. To address this issue, they looked at body fat percentage and lean mass index (LMI) and survival in 570 consecutive patients referred for cardiac rehabilitation. During three years of follow-up, 26 patients died.
Each patient was classified as low or high body fat (BF) and low or high LMI. There were 62 patients with low BF and low BMI; 53 with high BF and low LMI; 179 with low BF and high LMI; and 276 with high BF and high LMI.
Survival was worst for the low BF/low BMI group, 15% of whom died during follow-up, and best for the high BF/high LMI group, which had a 2.2% mortality rate.
Mortality was 5.7% for the high BF/low LMI group and 4.5% for the low BF/high LMI group.
The results were similar for men and women.
Patients with chronic obstructive pulmonary disease (COPD) had a particularly high mortality rate, of 18.5%, compared to 3.9% for patients without COPD. However, when the researchers adjusted for COPD in multivariate analysis, they found it did not independently predict mortality. Accounting for COPD "modestly weakened" the effect of LMI on mortality, but it did not affect the influence of BF.
High body fat and a better prognosis?
"Any time you have a higher lean mass you usually have good things going with it," Dr Lavie said. "What I think more surprising is that the high body fat is also associated with a better prognosis."
"We certainly don't want to give people the idea that it's better to be obese," Dr Lavie added. One message that doctors can take home from the findings, he said, is to advise their patients to build up their lean mass by eating better and getting enough exercise, including strength training.
(Reuters Health, September 2012)
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