More evidence has found that BMI is a rubbish indicator of fat content. The idea that overweight or obese people more often survive after heart failure, called the “obesity paradox”, is likely to be false, according to new research. By looking at waist-to-height ratio instead of body mass index (BMI), the researchers discovered that the mysterious correlation disappears, putting further question to BMI as a medical metric. Identified by a few different studies, there is an apparent correlation between higher BMI and survival after diagnosis of chronic heart disease, despite excess weight increasing the likelihood of developing the disease. It is counterintuitive and has long been questioned by scientists, with various explanations being put forward: some believe that fat could be protective against heart damage in some unknown way; while others believe the answer lies in BMI being a poor measure of obesity, as opposed to the obesity paradox being an actual health phenomenon. “It has been suggested that living with obesity is a good thing for patients with heart failure and reduced ejection fraction – which is when the main chamber of the heart is unable to squeeze out the normal amounts of blood. We knew this could not be correct and that obesity must be bad rather than good. We reckoned that part of the problem was that BMI was a weak indicator of how much fatty tissue a patient has,” said Professor John McMurray, lead author of the study, in a statement. To this end, a research team from the University of Glasgow looked to find a more representative measure of body fat. The researchers began by taking a diverse cohort of 1,832 women and 6,567 men who were hospitalized with heart failure and matched them with BMI scores, once again finding that higher-BMI patients fared better post-disease. They then went on to adjust these results for different measurements, mainly waist-to-height ratio, waist-to-hip ratio, and waist circumference, but also taking into account biomarkers such as natriuretic peptides, which are the best markers of heart failure according to the researchers. Once they controlled for these, the correlation quickly collapsed. They did, however, notice a strong correlation between high BMI, high waist-to-height ratio, and the onset of heart failure, indicating that it is an entirely negative relationship. The results indicate that BMI is not a strong indicator of obesity-related health risks, and researchers should explore other metrics as alternatives. The authors note that the study should look to more accurately take measurements and to take them over a longer period to adjust for any changes if they were to improve the findings, but they add to a growing body of evidence that BMI should probably be avoided in healthcare. “Would it be feasible to assume that an American professional wrestler (more muscle) and a Japanese sumo wrestler (more fat) with the same BMI would have a similar risk of cardiovascular disease? The same is true for persons such as Arnold Schwarzenegger in his younger years when he starred as the ‘Terminator’ with a BMI of ~30 kg/m2,” writes Professor Stephan von Haehling. The study is published in the European Heart Journal, along with an accompanying editorial. Source
