Obesity and Bone.

Joseph Proietto

doi:10.12688/f1000research.20875.1

Abstract

Obesity and osteoporosis are both common conditions with high rates of morbidity and mortality. There is a relationship between obesity and bone. There are multiple factors that influence the risk of fracture, including the quality of bone, the risk of falls, and the padding around the bone. These multiple factors partly explain the finding that obesity protects against fractures in some sites while increasing the risk in other parts of the body. While it is well known that increased weight builds bone, there are several mechanisms related to the obese state that make the bone more fragile. These include the increased production of bone marrow fat cells at the expense of bone-forming osteoblasts, an increase in inflammatory cytokines leading to the activation of bone-resorbing osteoclasts, mutations in the FTO gene, and obesity-induced increased osteoblast senescence. Surprisingly, the relationship between bone and obesity is not unidirectional; there is now evidence that osteocytes are able to regulate body weight by acting as weighing machines.

Highlights

Both obesity and osteoporosis are common conditions leading to increased morbidity and mortality
BMI was protective for hip with a hazard ratio (HR) of 0.8 (95% confidence interval [CI] 0.71–0.90), spine with a HR of 0.83, and for wrist with a HR of 0.88 (HR with 95% CI for each increase in BMI of 5 kg/m2)
Replacement of osteoblasts by fat cells in bone marrow Clinically, it has been found that situations leading to bone loss such as old age, thiazolidinedione treatment, and prolonged corticosterone treatment are associated with increased fat in bone marrow[15]

Summary

Introduction

Both obesity and osteoporosis are common conditions leading to increased morbidity and mortality. Despite more bone mass, obesity confers an increased risk of osteoporosis[11] and bone fractures[12], at least in some sites. Liu and colleagues in a cross-sectional study involving 471 women divided into normal, overweight, and obese groups found that there is a threshold effect of fat on bone density. They concluded that while body fat below 33% has a positive relationship with bone density, for body fat above 33% the relationship between fat mass and bone is negative for most skeletal sites[14]. How can obesity damage bone? Several mechanisms have been proposed for the deleterious effects of obesity on bone: 1. Replacement of osteoblasts by fat cells in bone marrow

Increased metabolism and accelerated senescence in stromal stem cells

Conclusion

Stuart-Jones V

24. Ferrante AW

Findings

31. Manolagas SC