Following the LABS-1 study, the LABS-2 study was initiated to examine the longer-term safety, outcomes, and durability of health changes of bariatric surgery. The primary objectives of the LABS-2 study were to determine weight, medical, surgical, and behavioral outcomes, including incidence and remission of co-morbid conditions, and to evaluate participant, procedure, and other characteristics that were associated with these outcomes. The study included participants who underwent bariatric surgery at LABS clinical centers through 2009. Clinical assessments, detailed interviews, and questionnaires were administered at several post-operative time points (30 days, 6 months, 12 months following surgery, and annually thereafter) to assess risks of surgery and changes in clinical, metabolic, and psychosocial characteristics in participants following bariatric surgery. Detailed data about the surgical procedure and peri- and post-operative care were also collected to determine if components of the surgical procedure, care, and/or clinical/demographic participant characteristics were associated with post-operative risks and changes in status.

An ancillary study from LABS-2 regarding psychosocial issues in bariatric surgery conducted psychological assessments of eating disorder symptomology and general psychopathology at three timepoints: approximately 2-3 weeks pre-operative, 2 months post-operative, and 8 months post-operative. Another ancillary study from LABS-2 regarding energy expenditure assessed whether activity thermogenesis increased in participants undergoing bariatric surgery post-operatively at 6 and 24 months compared to pre-operatively. Both ancillary studies are available in the data package for LABS-2 along with the full data.

The primary objectives were to use standardized techniques and measures to assess the longer term safety and efficacy of bariatric surgery by comparing post-surgical outcomes to pre-operative status, and examining risks and benefits of surgery.

The secondary objectives were to assess health care utilization of participants undergoing bariatric surgery for treatment of obesity and related co-morbidities, and to obtain and store specimens (serum, plasma, urine) for research related to the study and future research into the pathophysiology of obesity and obesity related complications.

Outcome measures include participant and procedure characteristics correlated with short- and long-term outcomes of bariatric surgery to evaluate the safety and efficacy of bariatric surgical procedures as treatment for participants with obesity and to identify risk factors. Additionally, changes in medical and psychosocial measures impacting the outcomes of bariatric surgery over time.

• Participants at least 18 years of age who undergo bariatric surgery by a LABS certified surgeon
• Selected by a site-specific sampling algorithm to be approached for inclusion in LABS-2

• Informed consent not obtained
• Prior bariatric surgery
• Unlikely to comply with follow-up protocol (e.g., travel time from home too long to make visits feasible, unwilling to return for follow-up visits)
• Unable to communicate with local study staff

Initial findings show that participants with severe obesity who underwent bariatric surgery experienced substantial weight loss 3 years following the surgical procedure, with the majority experiencing maximum weight change during the first year. The amount and trends of weight loss, diabetes, blood pressure, and lipid levels were variable.