In response to rapidly increasing rates of obesity, bariatric weight loss surgeries have increased worldwide, reaching approximately 341,000 procedures in 2011. Bariatric surgery is a major medical intervention with the primary goals of chronically reducing excess weight loss, decreasing incidence and severity of obesity related co-morbidities, and overall improvement in quality of life. Despite widespread evidence of bariatric surgery effectiveness on excess weight loss and resolution of co-morbidities, the effects of weight loss surgery on overall cardiorespiratory fitness and physical activity levels (two critical components of overall health) have yet to be defined. This book discusses the prevalence of bariatric surgery, as well as the complications and its impact on quality of life.