New research debunks the ‘obesity paradox’

A recent European Heart Journal (EHJ) study has finally solved the puzzle surrounding the “obesity paradox,” a concept suggesting that being overweight or obese may actually offer some protective health benefits [1]. 

The paradox has its roots in previous findings that people with a BMI indicating that they are overweight or obese had a lower risk of mortality from certain heart-related diseases than people of a healthy weight, according to the study’s authors. Combined with the tendency of people with severe and chronic illnesses to lose weight, the paradox led some researchers to posit that perhaps “extra fat” offers an advantage. 

However, the new EHJ study found the supposed protective effect of being overweight or obese is at least partially due to BMI’s unreliability as a measure of body fat. When the authors used waist-to-height ratio in place of BMI, the “survival advantage” for overweight people was far less pronounced, the authors found.

Our study shows there is no ‘obesity survival paradox’ when we use better ways of measuring body fat,” said John McMurray, professor of medical cardiology at the University of Glasgow in the UK, who led the latest research, in a statement about the study. “BMI does not take into account the location of fat in the body or its amount relative to muscle or the weight of the skeleton, which may differ according to sex, age and race. In heart failure specifically, retained fluid also contributes to body weight.”

Overall, the study analyzed data from over 8,000 people with heart failure in 47 countries across six continents, tracking which patients were hospitalized or died from heart failure. While those with BMIs of 25 kg/m2 or higher indeed had lower death rates, the difference disappeared when the researchers adjusted the results to take other relevant factors, such as the level of natriuretic peptides in the blood, into account. 

In fact, after adjusting for prognostic variables, BMI and waist-to-height ratio both showed that being heavier puts patients at higher risk. 

“After adjustment, both BMI and waist-to-height ratio showed that more body fat was associated with a greater risk of death or hospitalization for heart failure, but this was more evident for waist-to-height ratio. When looking at waist-to-height ratio, we found the top 20% of people with the most fat had a 39% increased risk of being hospitalized for heart failure compared to people in the bottom 20% who had the least fat,” said the study’s first author, Jawad Butt, a research fellow from Copenhagen University Hospital. 

The findings could have important implications for healthcare professionals and public health officials, who may need to reevaluate their approach to measuring and managing obesity-related health risks.

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