By John Kruse
Recently, Massachusetts stipulated that measurement of Body Mass Index (BMI) will be required in grades one, four, seven and ten in public schools. This new requirement is an attempt to do something about rising obesity rates in children. The program is slated to start this fall and was decided upon by the Massachusetts’ Public Health Council.
BMI is calculated by dividing weight (in kilograms) by height (in meters) squared. Required BMI screenings are certainly controversial. Critics often cite the shortcomings of the measurement with various ethnic groups. For this reason, the FITNESSGRAM assessment uses a criterion that is much more forgiving than the Centers for Disease Control’s (CDC) popular norm-referenced growth charts.
A recent study published in the April issue of the Archives of Pediatrics & Adolescent Medicine found that one in four preschoolers (4-year-olds) in the US are obese. The cut-off point to determine obesity was a BMI at the 95th percentile. According to the CDC’s growth charts a BMI at the 95th percentile for girls and boys is considered obese. Interestingly, the FITNESSGRAM criteria starts at 5-years-old (i.e.: they don’t have a standard for below age 5) and a BMI at the 95th percentile (approximately a BMI of 18) falls within FITNESSGRAM’s “Healthy Fitness Zone.” In other words, who are we to believe? CDC standards say these youngsters are obese. FITNESSGRAM standards suggest these children are healthy (assuming their BMI remains the same at age 5).
Other issues with BMI exist for individuals with athletic builds and a high percentages of muscle. Muscle weighs more than fat and its not uncommon for these individuals to have BMI scores suggesting they are overweight or obese. These issues will usually only pertain to adults since children haven’t experienced the hormonal changes necessary to build a significant amount of muscle mass.
While Massachusetts is requiring BMI screenings, they will also allow parents to opt out of the measurement. Perhaps parents in Massachusetts should be given the option of skin-fold measures of body composition due to the shortcomings of BMI. After all, if overall health is the objective, why not use a measurement that is calibrated off the gold standard–hydrostatic weighing.
Additional note: Check out FitMet’s free BMI Calculator and embed it on you website.
References:
http://www.cdc.gov/growthcharts.htm
Sarah E. Anderson; Robert C. Whitaker. Prevalence of Obesity Among US Preschool Children in Different Racial and Ethic Groups. Arch Pediatr Adolesc Med. 2009;163(4):344-348.