Damian McNamara

April 25, 2016

LOS ANGELES — A radiology-based measure of obesity more closely aligns with comorbidity risks than body mass index (BMI), according to a large retrospective study.

"BMI is a flawed measurement of obesity" because body shape and fat distribution can modify risk for related adverse health outcomes, said Albert Roh, MD, from the Maricopa Medical Center in Phoenix.

"We developed the fat-to-bone ratio to try to address those limitations, hoping to create a better measurement," he told Medscape Medical News. And it looks "promising," he added.

The results were presented in a poster here at the American Roentgen Ray Society 2016 Annual Meeting.

For their study, Dr Roh and his colleagues used 2703 upright posteroanterior chest radiograph examinations to calculate fat-to-bone ratio. Specifically, they measured soft tissue thickness over the acromioclavicular joints in both shoulders, and then divided by the diameter of the clavicle.

 
BMI is a flawed measurement of obesity.
 

They compared the fat-to-bone ratio with BMI to see if there were any significant differences in patient age, sex, or risk for common comorbidities associated with obesity.

Fat-to-bone ratio and BMI were both significantly associated with hypertension, diabetes, hyperlipidemia, obstructive sleep apnea, and osteoarthritis (P < .05). The occurrence of cerebrovascular accident was not significantly associated with either measure.

The associations between fat-to-bone ratio and obesity-related outcomes were significant, but between BMI and obesity-related outcomes were not.

Table. Association Between Obesity Measure and Related Outcomes

Outcome P Value for Fat-to-Bone Ratio P Value for Body Mass Index
Atherosclerosis .02 .90
Coronary artery disease .001 .42
Myocardial infarction .002 .25
Peripheral vascular disease .01 .50

 

BMI does not discriminate well between obese patients with fat primarily distributed around the chest or abdomen (an apple-like body) and fat primarily distributed on the hips (a pear-like body).

However, soft tissue measurements at the acromioclavicular joints correlate well with an "apple-like distribution" of fat and not muscle.

In terms of body composition, a person with a BMI of 30 m/kg² or more is considered obese, regardless of the amount of muscle or fat mass. However, "the muscular subject would not be predisposed to the comorbidities associated with obesity," Dr Roh and his colleagues point out.

In addition, the fat-to-bone ratio is easy to reproduce, they explain.

"Given that both fat-to-bone ratio and BMI were significantly associated with hypertension, diabetes mellitus, and hyperlipidemia, but only fat-to-bone ratio demonstrated high association with clinical conditions, such as atherosclerosis, coronary artery disease, myocardial infarction, and peripheral arterial disease, it will be of great benefit to clinicians in selecting out high-risk patients who will likely go on to develop these chronic conditions," said Karan Patel, MD, from Wayne State University in Detroit.

"I would be interested in seeing future prospective studies that look into establishing threshold values for each condition, which would help clinicians identify patients with multiple risk factors before they develop more serious disease," Dr Patel told Medscape Medical News.

"Our study was retrospective, but we hope to confirm the findings with prospective data in the future," Dr Roh reported.

Dr Roh and Dr Patel have disclosed no relevant financial relationships.

American Roentgen Ray Society (ARRS) 2016 Annual Meeting: Abstract E1215.

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