Fat mass link to bone density is gender and life-stage specific
MedWire News: Appropriate levels of body fat are essential for maintaining adequate bone mineral density, but the relationship is specific to gender and stage of life, research suggests.
"Osteoporosis and obesity, which are two representative disorders of body composition, share several common genetic and environmental factors," write Kyung Mook Choi (Korea University College of Medicine, Seoul) and colleagues in the Journal of Bone and Mineral Metabolism.
"Physical inactivity and aging induces both obesity and osteoporosis," they explain. "Moreover, these two disorders synergistically induce functional impairment and physical disability, making it important to clarify the precise underlying relationship between osteoporosis and obesity," they add.
In the present study, Choi and team analyzed data for 502 individuals (144 men, 159 premenopausal women, 199 postmenopausal women), aged 20-88 years.
The researchers used dual X-ray absorptiometry (DXA) and computed tomography to measure total body composition and fat mass, and DXA to measure bone mineral density in the lumbar region of the spine.
After controlling their results for the influence of age and body weight, the authors found that fat mass had no significant influence on bone status in men or postmenopausal women. In contrast, after the same adjustments, increased waist circumference, total fat area, subcutaneous fat area, appendicular fat mass, and percentage fat mass all significantly and independently predicted decreased bone mineral density in premenopausal women.
Of note, the inverse relationship between fat mass and bone mineral density persisted in premenopausal women after additionally controlling for the effects of physical activity pattern, alcohol intake, and smoking history.
The authors explain that "obesity is known as a systemic inflammatory condition, and adipose tissue secretes various inflammatory cytokines. Because inflammatory cytokines up-regulate the receptor activators of nuclear factor κB ligands, leading to bone resorption, low-grade systemic inflammation in obesity may reduce bone mineral density."
Regardless of the underlying processes, "these results suggest that if young women become obese, attainment of peak bone mass would be compromised, and this may be connected to a high risk of post-menopausal osteoporosis," the investigators conclude.
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By Philip Ford