Kristen and Lilly Grasso (Photo: Kristen Grasso, Facebook)

A Florida mom received an unpleasant surprise in the mail recently; no, it wasn't an unexpected bill, it was a letter that said her 11-year-old daughter, Lily, was overweight. "Lily is tall, she's athletic, she's solid muscle, Kristen Grasso, told Fox 4 News." By no means is she overweight." The girl, a star on her middle school volleyball team, had her Body Mass Index (BMI) calculated as part of a health screening mandated by Florida law. While parents can opt out, Grasso, a mother of four who says she tries to encourage her children to be active and feed them healthy meals, said when she received a notification about upcoming screenings she thought it would be about vision and hearing, not about weight.

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About 20 states have now adopted mandatory health screenings including weigh-ins to calculate the BMI of public school children in order to combat the childhood obesity epidemic. BMI is determined by multiplying a person's weight times their height squared, and it's widely used by physicians as an indicator of weight problems. Over the last 30 years in the United States, the rate of obese children has more than doubled and the rate of obese teens has tripled. But, some parents and children are concerned that sending home "fat letters," as they are derisively known, could lead to low self-esteem and bullying. Grasso said she was concerned for "kids that see the results of this test [who] may be classified as overweight but aren't, and the self-esteem issues that they may get."

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The Center for Disease Control says that children who have BMIs in the 85-95th percentile are considered to be overweight and the 95th percentile and above to be obese.

"I can understand the individual parent's angst," obesity expert Rexford Ahima, MD, PhD, of the University of Pennsylvania told Yahoo Shine. Ahima explains that measuring BMI is valuable for public health screenings, but not as a specific diagnostic tool. "It's useful when you are comparing populations," but doesn't distinguish factors such as gender, age, and ethnicity that may effect the result. BMI also doesn't measure body fat versus muscle mass. "Its not a true measure of health; some people may be classified as overweight but are very fit with no family history of, for instance, diabetes," and are therefore at low risk for developing diseases associated with obesity. Human error might also throw off the numbers. In Lily's case, the school measured her height to be 5"3' and weight to be 124 pounds, with a BMI of 22. Her mother says she's 5"5 which would make her BMI 20.8-within what the Centers for Disease Control considers to be its healthy range for children.

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However, despite BMI's limitations, Ahima says it's the best, cheapest tool we have for red flagging kids who might be at risk. "The intention to use it as a guide is ok, but in order to evaluate the information on an individual basis, then the child's physician should be involved."

Dyan Hes, MD, founder of Gramercy Pediatrics in NYC, who sits on the American Board of Obesity Medicine, agrees. "It's a screening tool, that's what people have to understand." She says that schools don't have the money to do MRI's or other sophisticated tests on each student to calculate their actual body fat. She points out that the letters aren't meant for children's eyes but for parents, and that they are an indication that schools are taking the obesity epidemic seriously. "We are waging a war on a disease that's devastating the next generation," she told Yahoo Shine. Hes says that mistakes are inevitable given the volume of students and limited resources, and that if a parent receives a letter indicating their child has a high BMI, they should have their child's physician perform a more detailed evaluation. "It's a conversation starter," she added.

Still, it's controversial topic. Lynn Grefe, President and CEO of the National Eating Disorders Association, says she's "totally opposed to BMI report cards." She says they can lead to discrimination, bullying, and actually encourage unhealthy eating behaviors in children who are labeled too heavy. "Our entire premise here at the National Eating Disorders Association is that we should be focused on health not weight," she told Yahoo Shine.

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