Dr. Arslanian and colleagues investigated how well waist circumference reflects total, abdominal subcutaneous, and visceral fat in youths and whether waist circumference predicts insulin resistance independent of BMI percentiles.

Waist circumference was an independent predictor of total body adipose tissue, total abdominal adipose tissue, visceral adipose tissue, and abdominal subcutaneous adipose tissue, the authors report. Waist circumference was marginally but consistently better at predicting these variables than was a combination of waist circumference and BMI.

Similarly, increasing waist circumference and BMI were associated with lower insulin sensitivity and higher fasting insulin and proinsulin. Waist circumference remained a significant correlate after controlling for BMI percentile and independently of race, the researchers note.

"These findings suggest that the influence of BMI percentile on total and abdominal adiposity and metabolic profiles are mediated through central obesity, measured by waist circumference, and that waist circumference alone is an independent predictor of total and abdominal adiposity and metabolic profiles," the authors conclude.

"The waist circumference may prove useful as an adiposity index, especially that measuring waist circumference requires only one measurement while that of BMI requires both weight and height measurements and calculation," Dr. Arslanian said. "At an epidemiological and public health level, waist circumference may be better. However, we need more studies."