Background: Patients satisfying the National Institutes of Health criteria and deemed appropriate candidates often do not undergo bariatric surgery for insurance-related reasons. Our objective was to explore the natural history of these patients compared with that of those who underwent laparoscopic Roux-en-Y gastric bypass (LRYGB). Methods: The medical records of the patients evaluated for LRYGB from 2001 to 2007 were retrospectively reviewed. The presence of co-morbidities was assessed at the initial evaluation and within a 3-year follow-up period for patients who had undergone LRYGB and those denied surgery. The statistical analysis included chi-square tests. Results: A total of 189 patients were in the denied cohort and 587 in the LRYGB cohort. The age, gender, and body mass index were similar between the 2 cohorts at the initial evaluation. The percentage of patients with a diagnosis of a co-morbidity in the denied and LRYGB cohorts at the initial evaluation was 20% and 25% with diabetes mellitus, 51% and 43% with hypertension, 20% and 22% with obstructive sleep apnea, 34% and 24% with lipid disorders, and 62% and 49% with gastroesophageal reflux disease, respectively. The body mass index at the initial evaluation and during follow-up was 47.3 and 46.8 kg/m(2) in the denied cohort (n = 165, P = .236) and 48.5 and 30.5 kg/m(2) in the LRYGB cohort (n = 544, P < .001), respectively. During the follow-up period, a greater incidence of new-onset diabetes (P < .001), hypertension (P < .001), obstructive sleep apnea (P < .001), gastroesophageal reflux disease (P < .001), and lipid disorders (P < .001) was observed in the denied cohort. Conclusion: Patients denied LRYGB had a greater incidence of new co-morbidities diagnosed within a short follow-up period, without a significant change in their body mass index. (Surg Obes Relat Dis 2010;6:591-596.) (C) 2010 American Society for Metabolic and Bariatric Surgery. All rights reserved.