Do gastric bypass patient characteristics, behavior, and health differ depending upon how successful weight loss is defined?

There is no standardized definition of "weight loss success" after bariatric surgery. The current study was designed to evaluate if various patient factors differed between those with successful and unsuccessful weight loss; and if these findings varied depending upon which definition of weight loss success was used. A chart review of psychiatric and medical files was conducted for 110 patients who had Roux en-Y Gastric Bypass and at least 1 year of follow-up data. Data were analyzed for four weight loss success criteria: body mass index (BMI) < 30 kg/m(2) (n = 60 patients), BMI < 35 kg/m(2) (n = 86), ≥70% excess weight loss (EWL; n = 75), and ≥ 50% EWL (n = 103). For each success criterion, we examined the differences in demographics, physical co-morbidities, and psychological conditions before surgery and behavioral noncompliance after surgery between patients who had and had not achieved successful weight loss. Weight loss success rates with these patients ranged from 55% to 94%, depending upon which criterion was used. Having sleep apnea before surgery differentiated successful and unsuccessful patients when using BMI < 30 kg/m(2) and ≥70% EWL only. A success criterion of ≥50% EWL can be used for any patient, although a more stringent definition of success (BMI < 30 kg/m(2)) could be used for patients with BMI 40-50 kg/m(2). Future research should be done to examine how patient health and behavior predicts differing definitions of weight loss success.