Secondary Logo

Journal Logo

Body composition and bone mineral density in premenopausal and postmenopausal obese women

Omar, Omar Husseina; Zaki, Moushira Erfanb; Youssif, Safenaz Youssifb; Hussein, Yehia Omara

doi: 10.1097/01.MJX.0000414710.98146.5d
ORIGINAL ARTICLES
Free

Background Bone mineral density (BMD) is strongly linked to body weight. Overweight exerts mechanical stress on the bone and prevents aging-induced decrease in BMD. Despite the positive association between BMI and BMD and bone mineral content (BMC), the role of fat distribution in BMD remains unclear. The aim of our study is to examine the relation between body composition and regional BMD in premenopausal and postmenopausal obese Egyptian women.

Materials and methods This cross-sectional study included 50 obese Egyptian women with a mean age of 52.9±10.9 years and BMI over 30. They were divided into a premenopausal group (n=21) and a postmenopausal group (n=29). Total and regional BMD and body composition were measured by dual-energy X-ray absorptiometry (Lunar). BMD was measured at the hip, lumbar spine, and total body (BMD and BMC). Anthropometric measurements were performed for all participants.

Results The premenopausal group had significantly higher total body BMD, BMC, and femur BMD than the postmenopausal group, whereas postmenopausal women had a significantly higher waist to hip ratio and trunk to total fat mass (FM) ratio than premenopausal women. The results of the multiple-regression analysis stepwise method showed that spine BMD, femur BMD, and whole-body BMD had significant correlations with the total lean mass (LM) and the trunk to total FM ratio in the postmenopausal women, whereas the total BMD was significantly correlated with the total LM only in the premenopausal women.

Conclusion It can be concluded that lean body mass is a significant determinant of BMD in premenopausal obese women, whereas both body lean and fat mass are significant determinants of regional and total BMD in postmenopausal obese women. The study suggests that LM and FM have an alternative impact on BMD in premenopausal and postmenopausal Egyptian obese women.

aRadiodiagnosis Department, Faculty of Medicine, Ain Shams University

bBiological Anthropology Department, Medical Research Division, National Research Centre, Cario, Egypt

Correspondence to Moushira Erfan Zaki, Biological Anthropology Department, Medical Research Division, National Research Centre, El-Bohouth Street, Dokki, 12311 Cairo, Egypt Tel: +33371362; fax: +33370931; e-mail: moushiraz@yahoo.com

Received October 9, 2011

Accepted November 25, 2011

Back to Top | Article Outline

Background

Obesity and osteoporosis are major public health concerns. Overweight exerts mechanical stress on the bone and prevents aging-induced decrease in bone mineral density (BMD) and fracture 1. The associations between obesity and osteoporosis have been studied in several previous studies, which have shown that obesity seems to moderate the effects of osteoporosis by increasing BMD. Bones adapt to prevalent loading conditions and skeletal loads at weight-bearing sites stimulate adaptive increases in bone density and geometry. Body weight is largely composed of two components: fat mass (FM) and lean mass (LM or fat-free mass) 2,3. The relative contribution of these two components to the variation in BMD has been highly contentious. Although some studies have suggested that LM, not FM, is associated with BMD, other studies have shown that FM, not LM, is an important determinant of BMD 3–9. The aim of this study is to determine whether LM is more important than FM as a determinant of BMD among Egyptian obese women and the influence of menopausal status.

Back to Top | Article Outline

Materials and methods

This study was designed as a cross-sectional investigation, and was performed on 50 obese Egyptian women aged between 30 and 70 years. All the participants were recruited from Ain Shams University, Faculty of Medicine, El-Demerdash Hospital. The study was carried out between January and June 2010. Total and regional BMD and body composition were measured by Lunar DPX prodigy, a General Electric dual-energy X-ray absorptiometry device, equipped with body composition software. BMD was measured at the radius, hip, lumbar spine, and total body (BMD and bone mineral content). Measurements were obtained and analyzed using standard protocols as provided by the manufacturer, and whole-body estimates of body FM, LM, and bone mass, and percentage of total fat, and lean as well as segments of regions of the body (right arm, left arm, trunk, right leg, and left leg) were estimated in three compartments for the determination of fat, soft tissue, and bone mass. Anthropometric measurements were performed for all participants including weight, height, waist, hip, and mid upper arm circumferences. The anthropometric measurements and instruments used followed the International Biological Programme 10. BMI was calculated according to the [weight (kg)/height (m)2] equation. Participants were divided into two groups according to the menstrual history: premenopausal group and postmenopausal group. All the participants answered a questionnaire on medical history, present medications, menopausal state, and age at menopause. Menopause was defined as no menstruation for more than 12 months or surgical menopause. Comparison of the premenopause and the postmenopause groups was performed using the Student t-test. The multiple-regression analysis stepwise method was used to determine the relative contribution of body composition variables toward total and regional BMD. Ethical approval and appropriate informed consent were obtained from all the participants.

Back to Top | Article Outline

Results

Comparisons of anthropometry, body composition, and total and regional BMD between premenopausal women (n=21) and postmenopausal women (n=29) are shown in Table 1. The premenopausal group had significantly higher total BMD, total bone mineral content, and femur BMD than the postmenopausal group. The waist to hip ratio and the trunk to total FM ratio were significantly higher in the postmenopausal group than the premenopausal group. The results of multiple-regression analysis between the total and regional BMD and regional body composition are shown in Tables 2 and 3 for premenopausal and postmenopausal women, respectively. Because body weight was a sum of FM, LM, and bone mass, we did not include body weight as an independent variable. As shown in Table 2, the total BMD correlated significantly with the total LM in premenopausal women. Table 3 shows that spine, femur, and total BMD had significant correlations with the total LM and the trunk FM ratio in postmenopausal women.

Table 1

Table 1

Table 2

Table 2

Table 3

Table 3

In the regression analysis, Fig. 1 shows a correlation between the FM ratio and BMD in postmenopausal women, and Fig. 2 shows a correlation between LM and BMD in premenopausal women.

Fig. 1

Fig. 1

Fig. 2

Fig. 2

Back to Top | Article Outline

Discussion

Osteoporosis is a major public health problem in developed countries. There are many factors that affect BMD. The relative contribution of LM and FM to BMD remains a contentious issue. Some studies have found a positive association between LM and BMD, and others have shown that FM is an important determinant of BMD 8,11. Distinguishing the role of LM versus FM as a determinant of BMD has clinical relevance; however, determination of the independent effects of LM and FM on BMD is not straightforward because the two measurements are correlated, and depending on the magnitude of correlation, when they are considered in a multiple linear regression model, it is sometimes impossible to differentiate one effect from another. It is well known that obese women have elevated BMD 12,13. This may be partially attributable to the effect of increased circulating estrogen levels derived from extraglandular secretion of androgen in adipose tissue and the increased weight-bearing effect of FM on BMD. Still other studies have found that both FM and LM are significant predictors of bone density, with LM being a more important predictor than FM in premenopausal women and FM being more important than LM in postmenopausal women 14,15. The association between BMD and LM suggests that an increase in physical activity may directly translate into protection against osteoporosis, whereas an association between BMD and FM implies that obesity may have a protective effect against bone loss. Factors that affect BMD do not always generally influence BMD throughout all stages of the life cycle. Some factors have a strong impact on BMD during a certain period of the life cycle and then have a reduced impact on BMD at other stages of the life cycle.

Our study showed that the menopausal state had a strong negative influence on total and regional BMD among Egyptian obese women (Table 1). Total BMD correlated significantly with total LM in premenopausal women and total and regional BMD correlated significantly with the total lean and trunk FM ratio in postmenopausal women (Tables 2 and 3).

Some studies have reported a positive correlation between FM and others have reported a correlation with fat-free mass. We examined the differential effects of FM and LM on BMD. Our results showed that both LM and FM were positively associated with BMD in postmenopausal women, which is consistent with previous studies 4,16,17. Our results disagree with other studies that reported that only lean body mass was correlated with BMD on multiple-regression analysis in postmenopausal women 18,19. Our results showed that body FM was best correlated with BMD in postmenopausal women, in agreement with previous reports 8,11,12. It was initially reported that FM was a major determinant of BMD 9. It is speculated that the loose relationship between lean body mass and BMD of the vertical axis may be partially attributable to the decreased physical activity in postmenopausal women. It appears that lean body mass does not become a significant determinant of BMD in a sedentary life style.

On the basis of these results, we conclude that lean body mass is a significant determinant of BMD in premenopausal women, whereas both LM and body FM are significant determinants in postmenopausal women. Our observation is in agreement with the previous reports showing that body FM has no direct influence on BMD in normal premenopausal women 20,21. However, our observation is not in agreement with the other studies that have reported that body FM does not play a major role in preventing bone loss 9,22. Some previous studies did not differentiate postmenopausal women from premenopausal women in their analysis. DeLaet et al.23, in a meta-analysis of 12 multinational cohorts including nearly 60 000 adult participants, showed that independent of sex, those with BMI more than 25 kg/m2 had significantly lower rates of hip, osteoporotic, and all fractures. Moreover, some studies have reported that femur BMD and geometric strength are greater with overweight in postmenopausal women, but they vary in proportion to LM (mostly muscle) and not to body weight or FM 24. Dytfeld et al. 25 have reported that both FM and LM are determinants of BMD in postmenopausal osteoporotic women, with site-specific differences. It appears that LM and FM have an alternative impact on BMD in premenopausal and postmenopausal women. The impact of lean body mass on BMD of the vertical axis attenuated after menopause. In summary, LM exerts positive effects on BMD in premenopausal obese women, and both FM and LM might contribute to BMD in postmenopausal obese women. The mechanism underlying this relationship is an important question to be addressed in bone biology.

Thus, it remains to be elucidated whether these differences are attributable to aging, menopause, and/or both. Further study is needed to examine this issue.

Figure

Figure

Back to Top | Article Outline

Acknowledgements

Conflicts of interest

There are no conflicts of interest.

Back to Top | Article Outline

References

1. Aloia JF, McGowan DM, Vaswani AN, Ross P, Cohn SH. Relationship of menopause to skeletal and muscle mass. Am J Clin Nutr. 1991;53:1378–1383
2. Ruff CB. Body size, body shape and long bone strength in modern humans. J Hum Evol. 2000;38:269–290
3. Li S, Wagner R, Holm K, Lehotsky J, Zinaman MJ. Relationship between soft tissue body composition and bone mass in perimenopausal women. Maturitas. 2004;47:99–105
4. Leslie WD, Weiler HA, Nyomba BLG. Ethnic differences in adiposity and body composition: the First Nations bone health study. Appl Physiol Nutr Metab. 2007;32:1065–1072
5. Liu JM, Zhao HY, Ning G, Zhao YJ, Zhang LZ, Sun LH, et al. Relationship between body composition and bone mineral density in healthy young and premenopausal Chinese women. Osteoporos Int. 2004;15:238–242
6. Salamone LM, Glynn N, Black D, Epstein RS, Palermo L, Meilahn E, et al. Body composition and bone mineral density in premenopausal and early perimenopausal women. J Bone Miner Res. 1995;10:1762–1768
7. Taaffe DR, Cauley JA, Danielson M, Nevitt MC, Lang TF, Bauer DC, et al. Race and sex effects on the association between muscle strength, soft tissue and bone mineral density in healthy elders: the health, aging and body composition study. J Bone Miner Res. 2001;16:1343–1352
8. Wang MC, Bachrach LK, Van Loan M, Hudes M, Flegal KM, Crawford PB. The relative contributions of lean tissue mass and fat mass to bone density in young women. Bone. 2005;37:474–481
9. Reid IR, Ames R, Evans MC, Sharpe S, Gamble G, France JT, et al. Determinants of total body and regional bone mineral density in normal postmenopausal women – a key role for fat mass. J Clin Endocrinol Metab. 1992;75:45–51
10. Hiernaux J, Tanner JMWeiner JS, Lourie JA. Growth and physique: anthropometry. Human biology: a guide to field methods. 1969 Oxford Blackwell Scientific:2–42
11. Reid IR. Relationships among body mass, its components and bone. Bone. 2002;31:547–555
12. Hassager C, Christiansen C. Influence of soft tissue body composition on bone mass and metabolism. Bone. 1989;10:415–419
13. Shiraki M, Ito H, Fujimaki H, Higuchi T. Relation between body size and bone mineral density with special reference to sex hormones and calcium regulating hormones in elderly females. Endocrinol Jpn. 1991;38:343–349
14. Gnudi S, Sitta E, Fiumi N. Relationship between body composition and bone mineral density in women with and without osteoporosis: relative contribution of lean and fat mass. J Bone Miner Metab. 2007;25:326–332
15. Khosla S, Atkinson EJ, Riggs BL, Melton LJ III. Relationship between body composition and bone mass in women. J Bone Miner Res. 1996;11:857–863
16. Hsu YH, Venners SA, Terwedow HA, Feng Y, Niu T, Li Z, et al. Relation of body composition, fat mass and serum lipids to osteoporotic fractures and bone mineral density in Chinese men and women. Am J Clin Nutr. 2006;83:146–154
17. Ho Pham LT, Nguyen ND, Lai TQ, Nguyen TV. Contributions of lean mass and fat mass to bone mineral density: a study in postmenopausal women. BMC Musculoskeletal Disord. 2010;11:59–68
18. Kirchengast S, Peterson B, Hauser G, Knogler W. Body composition characteristics are associated with the bone density of the proximal femur end in middle- and old-aged women and men. Maturitas. 2001;39:133–145
19. Bevier WC, Wiswell RA, Pyka G, Kozak KC, Newhall KM, Marcus R. Relationship of body composition, muscle strength and aerobic capacity to bone mineral density in older men and women. J Bone Miner Res. 1989;4:421–432
20. Drinkwater BL, Bruemner B, Chesnut CH III. Menstrual history as a determinant of current bone density in young athletes. JAMA. 1990;263:545–548
21. Ijuin M, Douchi T, Matsuo T, Yamamoto S, Uto H, Nagata Y. Difference in the effects of body composition on bone mineral density between pre- and postmenopausal women. Maturitas. 2002;43:239–244
22. Douchi T, Matsuo T, Uto H, Kuwahata T, Oki T, Nagata Y. Lean body mass and bone mineral density in physically exercising postmenopausal women. Maturitas. 2003;45:185–190
23. De Laet C, Kanis JA, Odén A, Johanson H, Johnell O, Delmas P, et al. Body mass index as a predictor of fracture risk: a meta-analysis. Osteoporos Int. 2005;16:1330–1338
24. Beck TJ, Petit MA, Wu G, LeBoff MS, Cauley JA, Chen Z. Does obesity really make the femur stronger? BMD, geometry and fracture incidence in the women’s health initiative-observational study. J Bone Miner Res. 2009;24:1369–1379
25. Dytfeld J, Ignaszak Szczepaniak M, Gowin E, Michalak M, Horst Sikorska W. Influence of lean and fat mass on Bone Mineral Density (BMD) in postmenopausal women with osteoporosis. Arch Gerontol Geriatr. 2011;53:e237–e242
© 2012 Medical Research Journal