Appendicular fat mass is main determinant of bone mass
MedWire News: In older women the distribution of fat mass has a greater influence on bone mass than does either obesity per se or lean mass, a study by Portuguese researchers has found.
Intriguingly, the volume of appendicular fat - ie, fat in the arms and legs - appeared to have an independent protective effect on bone mineral density (BMD).
"Our data comply with previous evidence suggesting that subcutaneous fat (appendicular fat mass) is more relevant than android fat mass (visceral fat) to bone health," write Elisa Marques (University of Porto) and co-authors in Menopause: The Journal of the North American Menopause Society.
Marques's team sought to examine the relationships between patterns of fat and lean tissue deposition and BMD in older women. They enrolled 100 White women, aged on average 68.7 years, who were healthy and not taking any medication known to affect bone.
All women were assessed using dual-energy X-ray absorptiometry as well as completing food diaries and having their physical performance measured.
The prevalence of obesity, osteopenia, and osteoporosis were 32.0%, 68.5%, and 7.9%, respectively. Obese women had significantly higher BMD than normal-weight women, and the cohort was physically active overall, reporting an average of 81 minutes of moderate-to-vigorous physical activity per day.
All measures of body fat were significantly associated with BMD at the femoral neck, report Marques et al. However, the associations were weakest for the android-to gynoid-fat ratio and the percentage fat mass.
Lean mass distribution was also significantly associated with BMD, explaining around 12% of variance in this parameter.
However, appendicular fat mass had the strongest influence on femoral neck BMD, explaining 23.4% of variance, after adjusting for a raft of confounders (age, height, age at menopause, potential renal acid load, physical activity, and knee muscle strength).
Indeed, each 1-kg increase in appendicular fat mass was associated with a 0.023-g/cm2 increase in BMD at the femoral neck.
"These data suggest a positive and interactive association of BMD with appendicular fat mass in healthy older women," Marques et al conclude.
"The fat-bone connection has relevant public health implications for the design of appropriate strategies to combat age-related bone loss because lower body mass is amenable to change and is therefore a potentially preventable risk factor."
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By Joanna Lyford