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This Article Full Text Full Text (PDF) All Versions of this Article: 90/4/1104    most recent ajcn.2009.28025v1 Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Ducher, G. Articles by Daly, R. M PubMed PubMed Citation Articles by Ducher, G. Articles by Daly, R. M Agricola Articles by Ducher, G. Articles by Daly, R. M

Overweight children have a greater proportion of fat mass relative to muscle mass in the upper limbs than in the lower limbs: implications for bone strength at the distal forearm^1,2,3

¹ From the Centre for Physical Activity and Nutrition Research, Deakin University, Burwood, Australia (GD and SLB); the Centre of Physical Activity Across the Lifespan, Australian Catholic University, Melbourne, Australia (GAN); the Department of Rheumatology and Clinical Immunology/Allergology, University Hospital Bern, Bern, Switzerland (PE); the Medical School, Australian National University, Canberra, Australia, and the Commonwealth Institute, Canberra, Australia (RT); and the Department of Medicine, The University of Melbourne, Western Hospital, Melbourne, Australia (RMD).

² Supported by the Commonwealth Education Trust (United Kingdom) and the Commonwealth Institute (Australia). RMD was supported by a National Health and Medical Research Council (NHMRC) Career Development Award (ID 425849), and SLB was supported by an NHMRC Career Development Award (ID 229320).

³ Address requests for reprints and correspondence to G Ducher, Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University, 221 Burwood Highway, Burwood, Victoria 3125, Australia. E-mail: gaele.ducher{at}deakin.edu.au.

Background: The influence of adiposity on upper-limb bone strength has rarely been studied in children, despite the high incidence of forearm fractures in this population.

Objective: The objective was to compare the influence of muscle and fat tissues on bone strength between the upper and lower limbs in prepubertal children.

Design: Bone mineral content, total bone cross-sectional area, cortical bone area (CoA), cortical thickness (CoTh) at the radius and tibia (4% and 66%, respectively), trabecular density (TrD), bone strength index (4% sites), cortical density (CoD), stress-strain index, and muscle and fat areas (66% sites) were measured by using peripheral quantitative computed tomography in 427 children (206 boys) aged 7–10 y.

Results: Overweight children (n = 93) had greater values for bone variables (0.3–1.3 SD; P < 0.0001) than did their normal-weight peers, except for CoD 66% and CoTh 4%. The between-group differences were 21–87% greater at the tibia than at the radius. After adjustment for muscle cross-sectional area, TrD 4%, bone mineral content, CoA, and CoTh 66% at the tibia remained greater in overweight children, whereas at the distal radius total bone cross-sectional area and CoTh were smaller in overweight children (P < 0.05). Overweight children had a greater fat-muscle ratio than did normal-weight children, particularly in the forearm (92 ± 28% compared with 57 ± 17%). Fat-muscle ratio correlated negatively with all bone variables, except for TrD and CoD, after adjustment for body weight (r = –0.17 to –0.54; P < 0.0001).

Conclusions: Overweight children had stronger bones than did their normal-weight peers, largely because of greater muscle size. However, the overweight children had a high proportion of fat relative to muscle in the forearm, which is associated with reduced bone strength.