Body fat more important than BMI in predicting type 2 diabetes risk, say experts

Healthcare professionals should account for body fat distribution in addition to body mass index (BMI) when screening people for prediabetes and type 2 diabetes, a new US study suggests.
Scientists have discovered that people with a normal BMI and high body fat are more likely to develop prediabetes or type 2 diabetes compared with those whose BMI is classed as overweight but who have a lower body fat percentage.
Researchers from the University of Florida now believe some people with normal BMI may have been neglected in preventative guidelines, and have called for greater consideration of body fat as a means of predicting diabetes.
The study involved a review of US adults aged 40 and older who had not been diagnosed with type 2 diabetes. They had their body fat percentage and BMI measured during 1999-2006 as well as their blood glucose levels. Overall, more than 65 million people were included within the data.
The analysis revealed that 13.5% of those with normal BMI and high body fat percentage developed prediabetes of type 2 diabetes, compared with only 10.5% of those deemed overweight by their BMI but who had low body fat.
“This high body fat percent link to abnormal blood glucose holds up even when we control for things like age, sex, race/ethnicity, family history of diabetes, vigorous-intensity exercise, and muscle strengthening activities,” said senior study author Arch G. Mainous III.
BMI helps to calculate whether a person is overweight by dividing their weight by their height, but its value as an accurate representation of health has been questioned because BMI does not distinguish between body fat and muscle mass. This is why muscular athletes may have a higher BMI because they have increased muscle rather than additional body fat.
“Typically, normal BMI has been perceived as healthy so people with normal BMI have been neglected in several preventive care guidelines,” said lead author Ara Jo, Ph.D. “Evidence has been mounting that BMI may not be the best measure of body fat for a variety of groups like individuals who are sedentary or older women.
“It also alerts us to consider ways of better identifying individuals with elevated body fat and incorporating it into clinical practice.”
The researchers hope their findings will be utilised to examine BMI more closely and examine its role in providing preventative care for those at risk of developing type 2 diabetes.
The findings appear online in the BMJ Open.