Obese patients, men in particular, are more likely to suffer bone fractures despite their high body weight, according to a new study published in the Journal of Clinical Endocrinology & Metabolism.¹

Jain et al enrolled 10,814 people in their study, aged 20-59 years, with an objective to investigate any link between the body composition and bone mineral density (BMD). For this, the dual x-ray absorptiometry (DXA) data and body composition data was obtained from the National Health and Nutrition Examination Survey (NHANES) 2011-2018. Lean mass index (LMI) and fat mass index (FMI) were used to assess body composition.

Out of a total of 10,814 included in the study, 3248 had obesity, 6795 were non-obese and 771 were severely obese. The non-obese participants tended to be younger in age.

Results showed that every 1 kg/m2 increase in LMI was linked to 0.19 higher T-score. On the other hand, every 1 kg/m2 rise in FMI was associated with 0.10 decrease in T-score. The effects of LMI were comparable in the male and female participants. However, the effect of FMI was more negative in men; 0.13 lower T-score per additional 1 kg/m2 of FMI in men vs 0.08 reduction in BMD T-score in women, respectively.

Body weight is an aggregate of lean mass and fat mass. Lean mass is the difference between the entire body weight and body fat weight.

In this study, a robust positive association was detected between lean mass and BMD in both men and women. However, the association between fat mass and BMD was found to be moderately negative and this negative association was stronger in men. Higher the fat mass, lower the bone density. The study authors do not rule out a possible role of fat distribution for the gender differences observed in their study.

Therefore, contrary to popular perception, high body weight should not be presumed to mean adequate BMD. Obese individuals should be screened for osteoporosis, particularly if risk factors such as older age, a past history of fracture, steroid treatment (current or previous) or a positive family history etc. are coexistent.

Reference

1. Jain RK, et al. Fat mass has negative effects on bone, especially in men: a cross-sectional analysis of NHANES 2011-2018. J Clin Endocrinol Metab. 2022 Feb 10;dgac040. doi: 10.1210/clinem/dgac040.