BMI
Almost very article you’ve read about the obesity epidemic relies on BMI to tell us who’s too fat, and who’s just right.
What we now call body-mass index dates back to 1832, when a Belgian mathematician named Adolphe Quetelet, Quetelet didn’t set out to study obesity; his goal was to standardize the use of statistics in social science.
Does BMI misclassify people?
BMI can’t distinguish between fat and lean tissue. Nor can it distinguish between different types of fat.
We know the visceral fat, the type that accumulates around your organs, puts your health in danger, whereas the fat women hold in their hips and thighs is linked to a lower risk of chronic health problems.
A person whose BMI says they are overweight or obese is often considered unhealthy, while people with normal BMI are often seen as healthy, but research published in 2016 suggested that this was incorrect for 75 million Americans.
Researchers found that 54 million Americans had been classed as overweight or obese, but cardiometabolic measures showed they were healthy. Another 21 million were classed as "normal" in terms of BMI, but they were unhealthy.
Misclassification of cardiometabolic health when using body mass index categories in NHANES 2005–2012
A J Tomiyama, J M Hunger, J Nguyen-Cuu & C Wells
International Journal of Obesity volume 40, pages 883–886 (2016)
A 2008 study in the International Journal of Obesity found that BMI underestimates the prevalence of obesity when you define it, as the World Health Organization does, as a body-fat percentage over 25 in men and 35 in women. Fifty percent of the people with a BMI in the normal or overweight ranges are actually obese.
BMI-related errors in the measurement of obesity
K J Rothman
International Journal of Obesity volume 32, pages S56–S59 (2008)
Muscle or fat?
One problem with BMI is that it does not distinguish between muscle and fat.
Consider this:
A person who does no exercise, is 1.83 meters, or 6 feet tall and weighs 92 kg, or 203 pounds (lbs), would have a BMI of 27.
An Olympic athlete, 1.83 meters, or 6 feet tall, and weighs 96 kilograms, or 211 lbs, would have a BMI of 28.
BMI is useful when studying populations and trends, however, it was never designed to be used as an individual health measure.
High body fat, not BMI, predicts diabetes
For this study, the scientists — led by Ara Jo, Ph.D., a clinical assistant professor in the Department of Health Services Research, Management and Policy at UF
The study focused on adults who had never been diagnosed with type 2 diabetes, and they used a scanning technique called dual-energy X-ray absorptiometry (DEXA) — which is the most accurate technique available — to measure body fat percentage.
They used the guidelines issued by the American Association of Clinical Endocrinologists and the American College of Endocrinology to estimate what counts as high body fat for men and for women.
According to these guidelines, having a percentage of body fat of 25 and above is considered high for men, and 35 percent is considered high body fat for women.
Based on these measurements, the analysis revealed that 13.5 percent of people with a normal BMI and a high body fat percentage had prediabetes or diabetes, compared with only 10.5 percent of those deemed "overweight" by their BMI but who had low body fat.
"This study provides more support for this idea of skinny fat and shows how percent body fat is more important in identifying individuals with prediabetes than BMI."
Arch G. Mainous III PhD
Almost very article you’ve read about the obesity epidemic relies on BMI to tell us who’s too fat, and who’s just right.
What we now call body-mass index dates back to 1832, when a Belgian mathematician named Adolphe Quetelet, Quetelet didn’t set out to study obesity; his goal was to standardize the use of statistics in social science.
Does BMI misclassify people?
BMI can’t distinguish between fat and lean tissue. Nor can it distinguish between different types of fat.
We know the visceral fat, the type that accumulates around your organs, puts your health in danger, whereas the fat women hold in their hips and thighs is linked to a lower risk of chronic health problems.
A person whose BMI says they are overweight or obese is often considered unhealthy, while people with normal BMI are often seen as healthy, but research published in 2016 suggested that this was incorrect for 75 million Americans.
Researchers found that 54 million Americans had been classed as overweight or obese, but cardiometabolic measures showed they were healthy. Another 21 million were classed as "normal" in terms of BMI, but they were unhealthy.
Misclassification of cardiometabolic health when using body mass index categories in NHANES 2005–2012
A J Tomiyama, J M Hunger, J Nguyen-Cuu & C Wells
International Journal of Obesity volume 40, pages 883–886 (2016)
A 2008 study in the International Journal of Obesity found that BMI underestimates the prevalence of obesity when you define it, as the World Health Organization does, as a body-fat percentage over 25 in men and 35 in women. Fifty percent of the people with a BMI in the normal or overweight ranges are actually obese.
BMI-related errors in the measurement of obesity
K J Rothman
International Journal of Obesity volume 32, pages S56–S59 (2008)
Muscle or fat?
One problem with BMI is that it does not distinguish between muscle and fat.
Consider this:
A person who does no exercise, is 1.83 meters, or 6 feet tall and weighs 92 kg, or 203 pounds (lbs), would have a BMI of 27.
An Olympic athlete, 1.83 meters, or 6 feet tall, and weighs 96 kilograms, or 211 lbs, would have a BMI of 28.
BMI is useful when studying populations and trends, however, it was never designed to be used as an individual health measure.
High body fat, not BMI, predicts diabetes
For this study, the scientists — led by Ara Jo, Ph.D., a clinical assistant professor in the Department of Health Services Research, Management and Policy at UF
The study focused on adults who had never been diagnosed with type 2 diabetes, and they used a scanning technique called dual-energy X-ray absorptiometry (DEXA) — which is the most accurate technique available — to measure body fat percentage.
They used the guidelines issued by the American Association of Clinical Endocrinologists and the American College of Endocrinology to estimate what counts as high body fat for men and for women.
According to these guidelines, having a percentage of body fat of 25 and above is considered high for men, and 35 percent is considered high body fat for women.
Based on these measurements, the analysis revealed that 13.5 percent of people with a normal BMI and a high body fat percentage had prediabetes or diabetes, compared with only 10.5 percent of those deemed "overweight" by their BMI but who had low body fat.
"This study provides more support for this idea of skinny fat and shows how percent body fat is more important in identifying individuals with prediabetes than BMI."
Arch G. Mainous III PhD
