Montclair State University faculty members Haiyan Su and Amir H. Golnabi are part of a groundbreaking study that could change the way obesity is diagnosed in adolescents.
The study, which was published today in the Journal of the American Medical Association Pediatrics, shows that tri-ponderal mass index (TMI) estimates body fat more accurately than the traditional body mass index (BMI) in adolescents. In essence, the BMI calculations that have been relied on for decades may not be an accurate scale for assessing body fat in adolescents between the ages of 8 and 17. These new findings are timely as diagnosing, treating and tracking the prevalence of children and adolescents with obesity is a high public health priority.
Su and Golnabi were part of the national team, consisting of researchers from Louisiana State University’s Pennington Biomedical Research Center, The University of Alabama at Birmingham, The United States Military Academy, The Albert Einstein College of Medicine and Verona University Medical School.
“In this study, we used careful statistical tests to find that the tri-ponderal mass index is more accurate for predicting body fat than BMI Z scores during adolescence,” says Su.
Obesity increases the risk of several chronic diseases in adults, including diabetes, cardiovascular disease and cancer. Children who are overweight are at an even higher risk than adults for chronic disease. With nearly one in six children in the U.S. classified as overweight, several national and global initiatives are now underway to screen and diagnose children as a first step in curbing the obesity epidemic and the chronic diseases that follow.
BMI is the standard measurement currently used worldwide to screen for obesity in both children and adults, despite prior evidence that it does not work as well in adolescents. To test BMI’s accuracy in adolescents, the researchers compared body composition data from 2,285 Caucasian individuals aged 8 to 29 who participated in the 1999-2004 U.S. National Health and Nutrition Examination Survey (NHANES).
The findings of the research team challenge the accuracy of BMI (weight in kilograms divided by height in meters squared) in adolescents aged 8-17 and show that TMI (weight in kilograms divided by height in meters cubed), estimates body fat more accurately than BMI in adolescents. Using current BMI percentiles, the researchers noted that adolescents are incorrectly diagnosed as overweight 19.4 percent of the time, versus only an 8.4 percent incorrect overweight diagnosis rate for TMI. The data showed this is especially true for lean adolescents, a significant fraction of whom are incorrectly being diagnosed as overweight.
The researchers also used mathematical strategies to show how the relationship between body weight and height is more complex in children and adolescents than it is in adults, particularly when adolescents are rapidly growing. The authors explained that for decades this complexity made it challenging to figure out the optimal body fat index for adolescents.
“The TMI model is much simpler and easier to understand for parents who may be dealing with an overweight child,” says Golnabi. “Utilizing such a tool would simplify the process of diagnosing children.”
The investigators agree that further research is needed to assess the effectiveness of TMI in broader audiences, including wider age ranges and ethnicities.
“While our findings are very informative and may impact how schools can effectively diagnose children with obesity, further investigations on other ethnicities should be conducted,” says Golnabi.
For more information on the study and its findings, visit http://jamanetwork.com/journals/jamapediatrics/fullarticle/2627569.