Obesity and fractures: between black and white aspects.

Obesity, a worldwide medical problem, associates a large panel of disorders but traditionally osteoporosis was not considered one of them. This mini-review targets human and animal studies related to this topic. DXA is the golden standard of fracture risk assessment by providing Bone Mineral Density (BMD) which is directly correlated to Body Mass Index (BMI). Recent studies found that the correlation become weaker at BMI >30 kg/sqm while associating a higher mechanical load. The obesity-related fracture risk includes a blunt bone turnover markers status and a proinflammatory environment as IL-6, TNF-a¾³. Common pathogenic pathways involve both the skeleton and the metabolic complications of obesity as growth hormone, insulin-like growth factor-1, angiotensin II and ghrelin. On the contrary, estrogens are fat-derived by aromatase conversion being bone protective as androgens or insulin resistance. Leptin and adiponectin are produced by adipose tissue playing multiple roles including on bone cells. The overlapping factors in obese persons that elevate the fracture risk are the vitamin D deficiency and sarcopenia with increased risk of fall and diabetic bone disease cause by the type 2 diabetes mellitus which is very frequent among obese subjects. Increased cortical porosity as well as alteration of bone matrix quality to the advanced glycation products is correlated to diabetic fracture risk while BMD remain inadequately normal. The correlation between obesity and fall also associates with prior diagnosis of chronic heart disease, severe depression/anxiety, chronic use of anti-depressants or sleeping pills, and sedentary lifestyle. A new map of fractures is drawn since obesity involves a higher risk of ankle (most frequent site in obesity) and humerus fractures and a lower risk of vertebral and hip fractures. The fracture healing is difficult in obese subjects due to inflammation and co-morbidities especially diabetes. Obesity has a rapidly rising prevalence so are the associated conditions; among them fragility fractures at specific sites represents an alarming new issue despite the traditional theories that obesity protects against osteoporosis.