Researchers at Mayo Clinic have found that people with normal Body Mass Index (BMI) who have the highest percentage of body fat are also at a risk of metabolic disturbances linked to heart disease.
The results are in contrast to the long-held belief that maintaining a normal weight automatically guards against disorders such as high levels of circulating blood fats and a tendency to develop metabolic syndrome, which often leads to type 2 diabetes.
The researchers defined "normal weight" by body mass index (BMI) as a condition of having a normal BMI with high body fat percentage.
"Using the term 'normal weight obesity' is really a way of being more precise about the changing conceptualization of obesity, because the real definition of obesity is excess body fat. Our study demonstrates that even people with normal weight may have excessive body fat, and that these people are at risk for metabolic abnormalities that lead to diabetes and, eventually, to heart disease," said Francisco Lopez-Jimenez, M.D., a cardiologist on the Mayo research team.
For the study, the researchers examined 2,127 adults, equally divided between men and women, who had normal weight (BMI between 18.5 and 24.9 units).
Later they assessed the participants' body composition, with their risk factors for metabolic and heart disease being collected by the U.S. government in its Third National Health and Nutrition Examination Survey.
Using this data, it was found that normal weight obesity was highly prevalent, affecting more than half of patients with a normal weight as defined by the BMI.
When they controlled for age, sex and race, it was found that normal weight obesity subjects had significantly higher rates of several alterations in blood chemistry that can negatively affect heart and metabolism health.
These markers of disregulation include altered blood lipid profile, such as cholesterol; high leptin, a hormone found in fat and other tissues and is involved in appetite regulation; higher rates of metabolic syndrome.
The study is significant, as heart disease remains the major cause of death and disability in Western countries.
The study suggested that the time has now come for a new measure of body fat.
"Combined, the data from our earlier work and the current study suggest it's time for a new measure of body fat as a risk factor of heart disease," said Dr. Lopez-Jimenez.
The results of this study will be presented at the American College of Cardiology's Annual Scientific Session next week in Chicago.