New York: Could the way doctors traditionally measure obesity allow a subset of people with obesity-related health risks slip through the cracks? Medical experts have typically calculated obesity using body mass index (BMI), a calculation based on a person’s height and weight.
A new study from Keck Medicine of USC, published in the Annals of Internal Medicine, quantifies how often BMI may miss cases of obesity. The research shows that one quarter of people considered to have a normal (healthy) BMI meet the standard of clinical obesity. And 50 percent of those deemed overweight by their BMI would be reclassified as obese.
“Many people assume that if their BMI says they are not obese, they don’t have to worry about the many health problems linked to obesity,” said Brian P. Lee, a hepatologist and liver transplant specialist with Keck Medicine and principal investigator of the study. “Our findings show that millions of Americans may already have obesity-related health impacts and may be missing needed health interventions.”
Those with normal or overweight BMIs do not currently qualify for pharmacologic or surgical treatments for obesity, and physicians may not necessarily flag them as needing lifestyle modifications that could improve their health, added Lee.
“BMI is problematic because it does not specifically measure body fat and instead reflects total body weight, which includes muscle and bone,” said Lee. “So a muscular person can have a very high BMI but not have excess fat, while someone without much muscle can have a normal BMI but have excess fat causing health problems.”
For the study, researchers used data from the National Health and Nutrition Examination Survey, a nationally representative survey of health and nutrition. They included data from some 5,600 adults with an average age of 49 who had been tested for both BMI and hip and waist circumferences.
When they compared BMI results with clinical obesity status, they reached the conclusion that approximately 26% of people with a normal BMI and 50% of people with an overweight BMI qualified as clinically obese.
In the future, Lee hopes that more physicians will diagnose obesity using the clinical obesity definition rather than BMI to better inform people of any health risks they may be facing.
