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Accounting for height in indices of body composition during childhood and adolescence

Correlations of body composition with height vary by age and sex during childhood. Standard approaches to accounting for height in measures of body composition (dividing by height (in meters)2) do not take this into account. Using measures of total body mass (TBM), fat mass (FM) and fat free mass (FFM) at ages nine, 11, 13, 15 and 18 years from a longitudinal UK cohort study (ALSPAC), we calculated indices of body composition at each age by dividing measures by height (in meters)2. We then produced age-and sex-specific powers of height using allometric regressions and calculated body composition indices by dividing measures by height raised to these powers. TBM, FM and FFM divided by height2 were correlated with height up-to age 11 in females. In males, TBM and FM divided by height2 were correlated with height up-to age 15 years while FM divided by height2 was correlated with height up-to age 11 years. Indices of body composition using age-and sex-specific powers were not correlated with height at any age. In early life, age-and sex-specific powers of height, rather than height in meters2, should be used to adjust body composition for height when measures of adiposity/mass independent of height are required.