Schools across America are increasingly taking it upon themselves to tell parents their children are obese, by mandating “report cards” that report students’ Body-Mass Index (BMI), a crude measure of height and weight. Critics of these “fat reports” (sometimes sent home in kids’ backpacks) see them as potentially life-changing for body-image-conscious youngsters, and not in a good way.

Last week a popular parenting blogger wrote that the nurse at her daughter’s elementary school sent home a “failing” BMI report card because the child fell within one index point of the government’s definition of “obese.” Jamie Lee is confident her “little girl” is healthy and fit, but indicates that the school’s “obesity” assessment is a lesson in how not to approach parents and children on this sensitive issue:

My daughter has always been solid as a rock. She’s all muscle and hardly ever stops moving. She’s not skinny, but she’s also not even an ounce overweight … The letter goes on to say, in bold type, that ‘only a physician can accurately determine whether an individual is underweight, overweight or obese.’ Damn straight. Then why are you sending me this scary letter with clearly erroneous information? What’s the point of that?

She points out a major flaw in BMI—it doesn’t differentiate between muscle and fat. A fit and toned athlete could be classified as “overweight” just looking at his or her BMI but would be in peak physical condition. Conversely, a sedentary child with poor eating habits could just as easily be designated in the "normal" range.

Health experts and nutritionists agree that BMI report cards are more effective at scaring parents and kids than helping anyone shed excess weight. Nutrition professors Linda Bacon and Paul Ernsberger both concur that measuring BMI fails to account for the emotional weight that falls on kids who are labeled (or mislabeled) as too fat:

[Ernsberger:] The idea of a BMI report card is horrible. To declare we're going to eliminate childhood obesity — that's actually a very stigmatizing thing to say. The overweight child hears that and thinks, ‘They wish I wasn't here.’

[Bacon:] It's done much more damage than good. The larger kids feel bad about themselves, and the thinner kids feel it doesn't matter whether they exercise or eat well.

It’s no wonder Dr. David Cundiff (writing in the International Journal of Obesity) recommends "abandoning the use of the BMI as a surrogate for physical inactivity and poor diet.” When some of the most chiseled professional athletes are classified as “obese” under BMI, common sense suggests that parents and kids should emulate superstars’ healthy dieting and exercise instead of fearing their BMI scores.