Body Mass Index Test for Preschoolers Inaccurate and Problematic

“We have to balance the fact that we have slightly imperfect measures, with the absolute importance of identifying these children.”


A new study published Friday in the New Zealand Medical Journal has criticized the Body Mass Index (BMI) tests in preschoolers, calling it “inaccurate and potentially harmful.”

BMI test helps to identify a few problems in preschoolers but registered dietician Lucy Carey, who was a part of the study, suggested it could be problematic doing so.

She explained that BMI can be inaccurate for some children, which may wrongly classify them as obese or overweight.

Carey said, “When parents are concerned a child is overweight, they’re more likely to restrict food for that child. You probably know if you’ve ever been on a restrictive diet yourself that you feel deprived and you seek out food more, and you almost become obsessed with food.”

“And it’s likely something like that is happening in children,” she added. “It’s actually causing them to gain more weight over time.”

Noting that BMI is more problematic for some ethnicities, Carey said, “Māori and Pasifika populations tend to be taller, and have more muscle. It’s quite flawed in that if you’re too tall and have a higher muscle to fat ratio, it overestimates how fat you are.”

The dietician said she wants to completely remove BMI tests from the pre-schooling check. Instead, she wants a more refined approach – such as counseling with parents and stressing the importance of eating home-cooked meals, getting adequate sleep, and limiting screen time.

Lead researcher and pediatrician Dr. Yvonne Anderson from the University of Auckland said, “BMI, while imperfect, is probably still the best measure available, and because of the country’s high levels of child obesity, early intervention and weight measuring shouldn’t be removed.”

“We have to balance the fact that we have slightly imperfect measures, with the absolute importance of identifying these children,” she added. “And addressing their weight-related health issues, and also trying to start that korero around healthy lifestyle change.”

However, Dr. Anderson explained it is important to change the conversation related to BMI testing in preschoolers. “The talk about healthy lifestyle change and how to make that persistent, and actually stopping using words like obesity, diet, and weight loss,” said Dr. Anderson. “Because I think they’re simply not helping in that korero around healthy lifestyle change.”