【听新闻练听力】Body Mass Index too vague, researchers say

>>> there is news tonight on this nation's growing weight problem. a problem that is getting worse because of how we measure it, especially when it comes to women.

>> reporter: it's no surprise that americans are getting fatter, but a new study finds the obesity epidemic could be a lot worse than anyone thought. the new face of obesity could actually look more like this. this is barbara, she's now at a healthy weight but a year ago, doctors determined she was obese. even though her body mass index indicated she was normal.

>> when i saw the results it was utterly shocking.

>> bmi estimates a person's body fat based on hight and weight alone. the widely used method is overly simplistic and underestimates the prevalence of obesity.

>> it doesn't tell you how much fat you have. that is the predictor of heart disease, cancer, stroke, gallbladder, fertility problems, depression, anxiety, sleep disorders, et cetera.

>> reporter: the study looked at 1393 adults. 48% of women were with misclassified as obese due to bmi. dr. braver man says april commonly used test to check for bone density is more accurate because it measures bone, muscle and fat. it also costs several hundred dollars. another approach is a simple blood test for leptin. a hormone associated with obesity.

>> that is costing the country a fortune for not measuring it. a dollar blood test and doing our bone density scans is going to pay off enormously.

>> reporter: barbara now says she's a new person, and has the proof inside and out. the fact that the bmi was introduced as a measure of obesity almost 200 years ago, just adds fuel to the fire that it's really outdated and truth be told. the same way americans got used to measuring ldl and hdl as part of a cholesterol