Bariatric surgery is considered as the only effective durable weight-loss therapy and may be curative for obesity-related comorbidities such as diabetes. Nevertheless this surgery is not devoid of potential long-term complications such as dumping syndrome, gastroesophageal reflux disease and nutrient deficiencies. For this reason, preoperative nutritional assessment and rigorous postoperative follow-up with administration of multi-vitamins supplements and assessment of serum levels is recommended for each patient who is undergoing a bariatric surgery. The aim of this review is to identify and treat the metabolic and nutritional complications of bariatric surgery.