Does obesity reduce risk for osteoporosis and fractures in older adults?

Fat as a Friend or Foe of the Bone

PURPOSE OF REVIEW

The objective of this review is to summarize the literature on the prevalence and diagnosis of obesity and its metabolic profile, including bone metabolism, focusing on the main inflammatory and turnover bone mediators that better characterize metabolically healthy obesity phenotype, and to summarize the therapeutic interventions for obesity with their effects on bone health.

RECENT FINDINGS

Osteoporosis and fracture risk not only increase with age and menopause but also with metabolic diseases, such as diabetes mellitus. Thus, patients with high BMI may have a higher bone fragility and fracture risk. However, some obese individuals with healthy metabolic profiles seem to be less at risk of bone fracture. Obesity has become an alarming disease with growing prevalence and multiple metabolic comorbidities, resulting in a significant burden on healthcare and increased mortality. The imbalance between increased food ingestion and decreased energy expenditure leads to pathological adipose tissue distribution and function, with increased secretion of proinflammatory markers and harmful consequences for body tissues, including bone tissue. However, some obese individuals seem to have a healthy metabolic profile and may not develop cardiometabolic disease during their lives. This healthy metabolic profile also benefits bone turnover and is associated with lower fracture risk.

Comparison of clinical risk factors for incident fracture in obese and non-obese community-dwelling older men

BACKGROUND

Obese older adults have higher bone mineral density (BMD), but other characteristics of obesity may predispose these individuals to fracture. We aimed to compare clinical risk factors for incident fracture in obese and non-obese older men.

METHODS

Body mass index (BMI) and body fat percentage were assessed at baseline by anthropometry and dual-energy X-ray absorptiometry, respectively, in 1625 community-dwelling men aged ≥70 years. Categories for non-obese and obese were <30 kg/m²and ≥30 kg/m² for BMI, and <30% and ≥30% for body fat percentage. Sociodemographic, medical, physical function and blood biochemistry parameters were collected at baseline. Self-reported incident fractures of any type and cause (excluding pathological fractures and fractures of hands, fingers, feet, toes and the skull) were confirmed by radiographic reports and recorded up to 9 years. Hip fractures were followed for 14 years using data linkage.

RESULTS

Prevalence of obesity was 27% according to BMI and 44% according to body fat percentage. There were no differences in incidence of any fracture between non-obese and obese men by BMI (10.7 vs 9.3%, respectively; P > 0.05) or body fat percentage (10.2 vs 10.6%, respectively; P > 0.05). Significant interactions were observed demonstrating that dementia increased hazard for incident any and hip fracture in non-obese men (adjusted hazard ratio 7.08; 95% CI 3.27-15.36 and 8.36; 3.13-22.31, respectively) but not obese men. Past-year falls increased hazard for any fracture in obese men (2.86; 95% CI 1.60-5.10) but not non-obese men while higher luteinizing hormone concentrations reduced hazard for hip fracture in obese men (0.91; 0.85-0.97 per IU/L) but not non-obese men.

CONCLUSIONS

In community-dwelling older men, obesity does not protect against incident fracture. Assessments of falls history and gonadotrophin levels, in addition to established clinical risk factors for fracture, may contribute to improvements in fracture prediction in obese older men.

Associations of Body Composition Trajectories with Bone Mineral Density, Muscle Function, Falls, and Fractures in Older Men: The Concord Health and Ageing in Men Project

Background

Weight loss increases fracture risk in older adults. We aimed to determine associations of 2-year body composition trajectories with subsequent falls and fractures in older men.

Methods

We measured appendicular lean mass (ALM) and total fat mass (FM) by dual-energy X-ray absorptiometry at baseline and Year 2 in 1,326 community-dwelling men aged ≥70 and older. Body composition trajectories were determined from residuals of a linear regression of change in ALM on change in FM (higher values indicate maintenance of ALM over FM), and a categorical variable for change in ALM and FM (did not lose [≥−5% change] versus lost [&lt;−5% change]). Bone mineral density (BMD), hand grip strength, and gait speed were assessed at Years 2 and 5. After Year 2, incident fractures (confirmed by radiographical reports) and falls were recorded for 6.8 years.

Results

Compared with men who did not lose ALM or FM, men who did not lose ALM but lost FM, and men who lost both ALM and FM, had reduced falls (−24% and −34%, respectively; both p &lt; .05). Men who lost ALM but did not lose FM had increased falls (incidence rate ratio = 1.73; 95% CI 1.37–2.18). ALM/FM change residuals were associated with improved lumbar spine BMD (B = 0.007; 95% CI 0.002–0.012 g/cm2 per SD increase) and gait speed (0.015; 0.001–0.029 m/s), and reduced hip fractures (hazard ratio = 0.68; 95% CI 0.47–0.99).

Conclusions

Fracture risk may be increased in older men who lose higher ALM relative to FM. Weight loss interventions for obese older men should target maintenance of lean mass.