The body mass index is not an accurate measure of body fat content and does not take into account critical factors to health or mortality such as fat distribution, proportion of muscle to fat and differences in body composition caused by sex or race, according to researchers.
Obesity is known to predispose a person to diabetes, heart diseases, sleep apnea, cancer and other diseases, according to background information in the article, which was published in the Aug. 23 issue of the journal Science. Although several studies have shown an increase in mortality in obese people, recent studies have suggested obesity in fact protects against death from all causes and death caused by chronic diseases such as diabetes, heart failure and stroke. The suggestion of a beneficial influence of obesity — dubbed the “obesity-mortality” paradox — has generated controversy.
Rexford Ahima, MD, PhD, and Mitchell Lazar, MD, PhD, addressed the challenges of measuring the health and mortality risks of obesity in a perspective article. Ahima and Lazar are with the Institute of Diabetes, Obesity and Metaboloism, part of the Perelman School of Medicine at the University of Pennsylvania in Philadelphia.
“There is an urgent need for accurate, practical and affordable tools to measure fat and skeletal muscle, and biomarkers that can better predict the risks of diseases and mortality,” Ahima said in a news release. “Advances to improve the measurement of obesity and related factors will help determine the optimal weight for an individual, taking into account factors such as age, sex, genetics, fitness, pre-existing diseases, as well novel blood markers and metabolic parameters altered by obesity.”
Obese BMI has a strong association with substantial increases in the risk of developing diabetes, cardiovascular diseases, cancer and other chronic diseases, leading to higher mortality, according to past research. However, studies have shown some people with obese BMI have an improved metabolic profile and reduced cardiovascular risk, and a subset of people with normal BMI are metabolically unhealthy and have increased mortality risk.
In the article, Ahima and Lazar point out the true effects of obesity may not be appreciated because population studies often describe associations of BMI and health and mortality risks without assessing how intentional or unintentional weight loss or gain affect these outcomes.
“Future research should be focused more on molecular pathways, especially how metabolic factors altered by obesity change the development of diabetes, heart diseases, cancer and other ailments, and influence the health status and mortality,” Lazar said in the release.
Article summary: www.sciencemag.org/content/341/6148/856.summary.