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Research suggests fat mass helps to build bone mass in girls
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Lean mass stimulates the increase of cortical bone mass in boys and girls, but fat mass plays a larger role in the accrual of cortical bone mass in girls, a recent study reported. Moreover, fat mass in girls appears to stimulate periosteal growth and suppress endosteal expansion.
Researchers for the Avon Longitudinal Study of Parents and Children found that although lean mass was the major determinant of bone mass, fat mass also exerted an important positive influence, especially in girls, in whom the effect was approximately 70% greater than in boys.
The study utilized tibial peripheral quantitative tomography to measure cortical bone mass, bone mineral content, bone mineral density, periosteal circumference and endosteal circumference at the mid-tibia in 4,005 boys and girls (mean age, 15.5 years).
Lean mass had a similar positive association with cortical bone mineral content in boys and girls (0.952; P=.85).
However, the means by which lean mass affected bone mass varied according to sex. Researchers reported a more positive association between lean mass and periosteal circumference in girls vs. boys (0.799 vs. 0.579; P<.0001). However, lean mass was only associated with cortical BMD in boys (0.443 vs. 0.014; P<.0001).
Compared with boys, girls had a stronger positive association between fat mass and cortical bone mineral content (0.227 vs. 0.355; P<.0001). According to the researchers, this finding reflected a greater positive association of fat mass with periosteal circumference in girls (0.312 vs. 0.213; P=.0002) and a stronger negative association with endosteal circumference (-0.181 vs. -0.059; P<.0001) compared with boys.
Previous study findings have been inconsistent regarding whether fat mass has a positive or negative effect on bone development.
“The effect of fat mass on bone mass appears to be strongest in girls,” researcher Jonathan Tobias, PhD, said in a press release. “Girls clearly have more fat mass than boys, and our findings show that whereas the greater lean mass in boys contributes to their greater cortical bone mass, this effect is partly counteracted by the greater fat mass in girls.”
Tobias added, “Fat mass in girls during puberty may have a long-term impact on bone health as they grow into adulthood. Excessive reduction in fat mass could have adverse effects on the developing skeleton — particularly in girls — leading to an increased risk of osteoporosis in later life.”
Tobias JH. J Clin Endocrinol Metab. 2010;95:699-706.