New type of weight measurement more accurate than BMI in teenagers

Researchers from the University of Alabama have found that triponderal body mass index (TMI) may be more accurate than BMI in estimating body fat amongst adolescents. In a study published in JAMA Paediatrics the researchers found that during adolescent development, weight was not proportional to height squared, which is the calculation for BMI. By examining data from 2,285 children and adolescents, in the Nutrition and Health Examination Survey, they found that TMI estimated body fat better than BMI. TMI itself is calculated by dividing weight by the cube of the height, they also reported that comparing TMI was much easier as it did not involve complicated percentiles, as comparing BMI does.

One particular area that the authors found BMI to be worse than TMI was the incorrect diagnosis of overweight. BMI calculations would do this 19.4% of the time, whilst TMI would result in 8.4% incorrect diagnoses, this data is especially important in lean adolescents. The authors stress that tracking body fat through adolescence is difficult as there is a complex relationship between height and weight due to the commencement of puberty. Further to this they highlighted that TMI should be considered in the context of other health and demographic factors. It is hoped that more research will be undertaken to assess the accuracy of TMI in a wider range of ethnicities and age ranges.