11 May 2012

BMI puts young Asian-American women at risk of being "skinny fat"

As if we needed any more reason to pick on Body Mass Index (BMI): new research finds that this most accepted approach for assessing overweight and obesity based on height and weight could lead to misclassification of young Asian-American women as healthy when they're really "skinny fat," which could put them at greater risk for type 2 diabetes and cardiovascular disease.

In my last post, I discussed the scary, growing problem of sarcopenic obesity (aka "skinny fat") in older adults, described as age-related muscle loss in combination with the accumulation of body fat. One common result of sarcopenic obesity is a misclassification using BMI as "normal-weight" in these aged individuals. Misclassification in older adults with sarcopenic obesity is just one reason why BMI is loathed by those interested in public health.

Sadly, I learned at Experimental Biology, misclassification also occurs frequently across all ages depending on ethnicity. Asian Americans with normal weight sarcopenic obesity, for example, are often misclassified even in a college-aged population, according to nutritional epidemiologist Catherine Carpenter, an associate professor from University of California, Los Angeles.

In a symposium organized by the American Society for Nutrition to discuss the topic of obesity and BMI classification, Carpenter presented findings of a yet-to-be-published cross-sectional study that evaluated BMI and percent body fat measured by biolectrical impedance analysis among on the multi-ethnic college students on campus. The study's findings were that college-aged Asian American women were most likely to be misclassified by BMI.

Kindly, Carpenter provided me with further details about the study after the event. The study included 940 college students recruited over four consecutive years. The average participant was 21.4 years old with an average normal weight BMI of 22.9 kilogram over meter squared (kg/m2). The average percent body fat was 24.8 percent. The ethnic samples consisted of four ethnic groups: 49 percent Asian, 23 percent Caucasian, 7 percent Hispanic, and 21 percent as Other.

Among the college-age students, Asian-American women had the lowest BMI (21.5 kg/m2), but the second highest percent body fat (27.8 percent). In comparison, Hispanic women had the highest percent body fat (29.9 percent) and the highest BMI (23.5 kg/m2).

These findings suggest Asian-American women are most likely to be misclassified by BMI, which could mean greater likelihood risk of normal-weight obesity gone unnoticed. Ultimately, greater risk of obesity-related chronic disease such as type 2 diabetes and cardiovascular disease is the result.

No question, studies like these will continue to reveal the limitations of BMI. Once again, I'll repeat that it may be better to focus physical activity and amount of skeletal muscle mass (along with or maybe more than dietary calories or macronutrients like sugar) for prevention of obesity and chronic disease.

Skeletal muscle is critical as a large site for fat burning, glucose disposal, and metabolic rate. Sarcopenia in college-age adults should be most disturbing! It's much easier to hold on to muscle than it is to gain it back. Prevention, as usual, is key; and, prevention can be achieved with daily physical activity and a balanced diet -- with sufficient daily intake of quality protein, especially after exercise and throughout the day.


1 comment:

eyecandy_babydoll said...

It's true, I have "underweight BMI" of 17.3 and yet I've always been this weight since I was in my late teens. Despite this doctors keep telling me I'm underweight and need to eat more (I do already!) to get back into the normal BMI range. Women from where I'm from (tropics of Asia) all weigh and look like my body shape. I only get the "you're underweight" issue when I'm in Australia. All my female Asian friends in Australia are slowly piling on the pounds as they age - yet their BMIs are considered normal. So I don't even bother with the BMI anymore. What I care about is maintaining muscle.