Few studies have demonstrated the risk of metabolic bone disease and a reduction in bone mineral density (BMD) after bariatric surgery. A systematic review was conducted of case-control and cohort studies with the aim of evaluating the relationship between bariatric surgery and bone metabolism. The search was undertaken in MedLine, covering the period from January 1997 to August 2009, using the keywords: "bariatric surgery" AND "osteoporosis", "fracture", "bone diseases", "metabolic". Six studies were included, comprising four cohort and two case-control studies. Three studies evaluated bone metabolism and BMD, and the other evaluated bone metabolism only. Based on this review, bariatric surgery is associated with alterations in bone metabolism, loss of bone mass and an increased risk of fracture. However, the maximum evaluation period covered by these studies was two years after surgery, hence the need to undertake further studies of longer duration in order to achieve a more thorough understanding of this association.