tri-ponderal mass index

A recent study published in JAMA Pediatrics suggests that tri-ponderal mass index is more accurate and simpler than body mass index for assessing body fat percentage in adolescents.


Body Mass Index (BMI) is a parameter used to assess if a person is overweight or obese. It is measured by dividing an individual’s weight by their height squared. In pediatrics, BMI z-scores are used to assess if a child is overweight or obese. Z-scores classify children as overweight or obese depending on their BMI percentile because weight in children is not proportionate to their measured height.

In an article published in the JAMA Pediatrics, a group of researchers conducted a cross-sectional study to determine if tri-ponderal mass index (TMI), calculated by dividing weight by height cubed, is a better method than BMI for assessing body fat percentage in adolescents. A total of 2285 non-Hispanic white males aged 8 to 29 years were included in the study. Dual x-ray absorptiometry and anthropometric data were used to assess changes in body proportions, height, weight, and percentage of body fat among different age groups. A variety of statistical analyses were then used to assess the accuracy of TMI and BMI for estimating body fat percentage to classify an individual as normal weight, overweight, or obese.

The results show that the percentage of body fat varies depending on the person’s height and age during adolescence. Between age 8 and 17, TMI estimated body fat more accurately than BMI and BMI z-scores. Using TMI also reduced the rate of misclassification as normal weight, overweight, or obese in this age group.

The study shows that using the TMI is a more accurate and simpler method for assessing body fat among adolescents. Further studies assessing the accuracy of using TMI in a larger study population and other ethnic groups should be done before introducing the method to clinical practice.


Written By: Karla Sevilla

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