Metabolically healthy obese concept overturned
medwireNews: A study of 3.5 million people strengthens the evidence against the notion that obesity is only a health risk if people also have metabolic abnormalities.
The research is published in the Journal of the American College of Cardiology, and was presented at the European Congress on Obesity earlier this year. In line with previous smaller studies, this one found that, during follow-up averaging 5.4 years, overweight and obese people who had no metabolic abnormalities had a cardiovascular disease risk that was intermediate between that of healthy normal-weight people and obese people with metabolic abnormalities.
The study involved UK residents who were aged an average of 44.7 years and free of cardiovascular disease at baseline, identified in The Health Improvement Network. Although this makes the results mostly relevant to a predominantly Caucasian population, and the researchers could not account for changes in BMI and metabolic health over time, the authors of a linked editorial describe the study as “pivotal.”
Jennifer Bea and Nancy Sweitzer, from the University of Arizona, Tucson, USA, stress that this is the “largest and most conclusive” study to address the issue of metabolically healthy obesity.
There are two key findings. The first is that, among people with no metabolic abnormalities (diabetes, hyperlipidemia, or hypertension), obese people had risk increases of 49%, 7%, and 96%, for CHD, cerebrovascular disease, and heart failure, respectively, relative to normal-weight people. Overweight people had significantly increased risks for CHD and heart failure, and underweight people had increased risks for cerebrovascular disease and heart failure.
The second finding is that metabolic abnormalities significantly increased cardiovascular disease risk even for people who were a healthy weight, with risk increases starting at around 1.5-fold for one abnormality and rising to around 2.5-fold for all three abnormalities.
The editorialists highlight this point, saying that such risk increases are “not inconsequential,” yet one or two metabolic risk factors are often “dismissed as unimportant” in normal-weight people. And they note that around 10% of the normal-weight people in the study had at least one abnormality.
“The study not only definitively countered the concept of metabolically benign obesity, but also demonstrated great risk to normal weight individuals if metabolic dysfunction is present,” say Bea and Sweitzer. “Thus, we would suggest an increased need for screening in the normal weight population.”
As expected, G Neil Thomas (University of Birmingham, UK) and study co-authors found that cardiovascular risk increased even more for overweight and obese people with one or two metabolic abnormalities. People with three abnormalities had the highest risk irrespective of their bodyweight, except in the case of heart failure where obese people had the highest overall risk, rising further with increasing number of metabolic abnormalities.
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