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Reformulation of BMI and Percent Body Fat to Remove the Height Bias in 8‐year‐olds
Author(s) -
Telford Richard D.,
Cunningham Ross B.
Publication year - 2008
Publication title -
obesity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.438
H-Index - 199
eISSN - 1930-739X
pISSN - 1930-7381
DOI - 10.1038/oby.2008.332
Subject(s) - overweight , percentile , medicine , body mass index , obesity , childhood obesity , endocrinology , dual energy , fat mass , demography , mathematics , statistics , bone mineral , osteoporosis , sociology
BMI and percent body fat (%BF) are both related to height (Ht) in prepubertal children, so may misrepresent childhood adiposity, especially in tall or short children. We sought to construct replacement functions for BMI and %BF that are independent of Ht. Fat mass (FM) was measured using dual‐energy X‐ray absorptiometry, together with Ht and body mass (BM) in 746 healthy boys and girls aged 8 years (0.34 s.d.). Relationships between BM, FM, and Ht were measured and values of p and q derived such that the functions BM. Ht − p and FM.BM − q were unrelated to Ht. BM was not directly proportional to Ht 2 , BMI being significantly related to Ht in both boys and girls ( P < 0.001). BM was proportional to Ht 3 , BM. Ht −3 being independent of Ht. Similarly, FM was not directly proportional to BM and %BF was significantly related to Ht ( P < 0.001). While FM was proportional to BM 2 , FM.BM −1.5 was the function found to be independent of Ht. Using the 85th and 95th percentiles as the cutoffs for overweight and obesity respectively, 6.4% of the boys and 6.8% of the girls were classified differently by BMI and the Ht independent measure BM. Ht −3 . Similarly, 10.1% boys and 13.7% girls were classified differently by %BF and the Ht independent measure FM.BM −1.5 . We propose that improved diagnostic accuracy of body composition in 8‐year‐olds is provided by the BM function (BMF, BM. Ht −3 ) and FM function (FMF, FM.BM −1.5 ) replacing BMI and %BF, which both overestimate the adiposity of taller children and underestimate it in shorter children.