Obesity has become one of the greatest public health concerns in the world. Obesity increases morbidity and mortality, and causes costs to society. Conventional therapy is ineffective, and the long-term results are poor. Bariatric surgery is proven to be effective and safe. 

The aim of this thesis was to identify the findings in upper gastrointestinal endoscopy (UGI) prior to laparoscopic Roux-en-Y Gastric Bypass (LRYGB) and to investigate the safety of enhanced recovery after surgery (ERAS) protocol in a general hospital. In addition, this study aimed at evaluating the prevalence of obstructive sleep apnoea (OSA) in bariatric surgery candidates and to investigate the effect of LRYGB on OSA at 12 months postoperatively. 

The most common findings in UGI were hiatal hernia and gastro-oesophageal reflux, which are relative contraindications for sleeve gastrectomy (SG), but not for LRYGB. According to this study, a routine UGI is not needed prior LRYGB, but may be indicated prior to SG. 

A systematic use of ERAS protocol reduced the length of hospital stay from two days to one day. At the same time overall morbidity and major complications decreased. 

The prevalence of OSA in bariatric patients was 71%, which decreased to 44% after surgery. OSA was resolved in 54% and resolved or improved in 90% of the patients. LRYGB is an effective treatment for OSA, but postoperative cardiorespiratory recordings are recommended in order to identify the approximately 20% of patients with persistent OSA.