Percent fat mass is inversely associated with bone mass and hip geometry in rural Chinese adolescents

Abstract

This study was an attempt to examine the phenotypic, genetic, and environmental correlations between percent fat mass (PFM) and bone parameters, especially hip geometry, among 786 males and 618 females aged 13 to 21 years from a Chinese twin cohort. PFM, bone area (BA), bone mineral content (BMC), cross-sectional area (CSA), and section modulus (SM) were obtained by dual-energy X-ray absorptiometry. Multiple linear regression models were used to assess the PFM-bone relationships. A structural equation model for twin design was used to estimate genetic/environmental influences on individual phenotype and phenotypic correlations. After controlling for body weight and other pertinent covariates, we observed inverse associations between PFM and bone parameters: Compared with the lowest age- and gender-specific tertile of PFM, males in the highest tertile of PFM had lower measures of whole-body-less-head BA (WB-BA), lumbar spine BA (L2–L4-BA), total-hip BA (TH-BA), total-hip BMC, CSA, and SM (p < .005 for all, adjusted p < .05). Similar inverse associations were observed in females for all the preceding parameters except WB-BA and L2–L4-BA. These associations did not vary significantly by Tanner stages. In both genders, the estimated heritabilities were 80% to 86% for BMC, 67% to 80% for BA, 74% to 77% for CSA, and 64% for SM. Both shared genetics and environmental factors contributed to the inverse PFM-bone correlations. We conclude that in this sample of relatively lean Chinese adolescents, at a given body weight, PFM is inversely associated with BA, BMC, and hip geometry in both genders, and such associations are attributed to both shared genetic and environmental factors. © 2010 American Society for Bone and Mineral Research.

Fat mass is a positive predictor of bone mass in adolescents

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We read the recent paper by Hong and colleagues (1) with interest because the title of this original article suggests an inverse association between fat mass and bone mass on hip geometry in adolescents. This is in direct contradiction to three large studies we have carried out on the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort using different methods to examine the association between fat and bone in adolescents.

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Nutrição e outros aspectos relevantes para a saúde óssea na adolescência

“…Alguns estudos mostram que a massa gorda é um preditor direto da massa óssea, [41][42][43][44][45] enquanto outros estudos mostram associação inversa entre essas massas em crianças e adolescentes (Tabela 1). [46][47][48][49][50] A falta de consenso pode ser parcialmente atribuída a diferentes abordagens estatísticas, especialmente a adoção de diferentes variáveis de ajuste, e ao fato de que a associação entre a DMO e massa gorda parece depender do sexo da população estudada. Alguns estudos mostram ausência de associação ou associação inversa entre a massa gorda e a massa óssea em adolescentes do sexo masculino, [45][46][47] enquanto que nas adolescentes, a massa gorda associa-se diretamente com a massa ós-sea.…”

“…Estudos recentes têm mostrado que, após o ajuste pela massa corporal total, a associação entre a massa de gorda e parâmetros da massa óssea torna-se inversa em crianças e adolescentes. [48][49][50] Por outro lado, tem sido demonstrado na literatura que, quando a massa magra é considerada como variável de ajuste, a massa gorda associa-se diretamente a ela. 44 …”

Response to “fat mass is a positive predictor of bone mass in adolescents”

“…(6,7) To date, the findings on the relationship between fat mass and bone phenotypes are conflicting in the literature. The aim of our study (8) was to examine the relationship between fat mass and bone phenotypes after accounting for a mechanical loading effect and other potential confounders.To this end, we believe that adjustment for total body weight [or body mass index (BMI)] best accounts for interindividual difference in overall mechanical loading. Furthermore, adjustment of total body weight also serves the purpose of correcting for the influence of body size on bone in children and adolescents.…”

“…(6,7) To date, the findings on the relationship between fat mass and bone phenotypes are conflicting in the literature. The aim of our study (8) was to examine the relationship between fat mass and bone phenotypes after accounting for a mechanical loading effect and other potential confounders.…”