Association between body composition and bone mineral density in healthy, non-obese, young Romanian adults and effects of menopause.

INTRODUCTION: The link between bone mass and body composition is widely recognized, but the mechanism remains unclear. Most studies enrolled subjects irrespective of their body weight and only few works were selectively performed on healthy subjects with body mass index (BMI) within normal limits.
MATERIAL AND METHODS: We aimed to determine the relevance of body composition parameters to bone mass in healthy, young and non-obese Romanian volunteers (n=42) and in postmenopausal women (n=20) and to establish the effects of menopausal transition. Both bone mineral density (BMD) and body composition were assessed using whole-body dual X-ray absorptiometry (DXA). OUTCOMES: Despite normal mean BMI, large variability of the whole-body fat mass (FM) content was noted, ranging between 18.6-49.7% in women and 22-40.3% in men. Fat mass was not related to bone density; in contrast, BMD at all sites was positively associated to fat-free mass (FFM) in young non-obese women (r=0.34-0.53). In women, the trunk fat mass/leg fat mass ratio was significantly predicted by age (p=0.001), explaining about 20% of the pattern variability. Menopausal status appeared not to significantly influence whole-body fat or FM distribution. A tendency towards a higher trunk FM/legs FM ratio was observed after menopause, but lost after age-adjustment.
CONCLUSION: In non-obese subjects, even of young age, the FM content and distribution is highly variable. FFM mass appears to be the main composition contributor to bone mass, at least in young, healthy, non-obese women. Menopause is not associated to major changes of whole-body fat and trunk adipose tissue, although a significant decrease in peripheral FM content and a tendency towards an age-dependent central redistribution of adiposity is noticed.