Background: The authors studied a range of preoperative factors for their predictive value of effectivenes of Lap-Band® placement, using the percentage of excess weight loss at 1-year as the outcome measure (%EWL1). Methods: All factors were measured and recorded prior to surgery. Factors included: patient demographics, family, medical and weight history. Laboratory measures and the responses to the SF36 Health Survey were also assessed. Factors were assessed for correlation with %EWL1. Results: The group (N=440, F:M 383:57) had mean age 40.0 ± 9.5 years, weight of 126 ± 25 kg, and BMI 45.6 ± 7.5 kg/m2 pre-operatively. At 1-year follow-up, the group had mean weight 97.6 ± 20 kg, BMI 35.6 ± 6.3 kg/m2, and %EWL1 45.8 ± 17%. Increasing age (R=-0.13, p<0.01) and preoperative BMI (R=-0.22, p<0.001) were significantly associated with less %EWL1 and all other factors were controlled for these before assessing significance. Important factors associated with a lower %EWL1 included: hyperinsulinemia (R=-0.36, p<0.001), insulin resistance (R=-0.33, p<0.001) and disease associated with insulin resistance, poor physical ability, pain, and poor general health responses to the SF-36 Health Survey. Patients who consumed alcohol regularly had a better rate of weight loss (R= 0.23, p<0.005). Factors that had no influence included gender, a history of mental illness and measures of mental health, previous bariatric surgery, and a history of many medical conditions associated with obesity. Conclusion: Important physical factors have been found to influence the rate of weight loss.Those with increased age, pain, physical disability and insulin resistance have a great deal to gain from weight loss. Although this study has identified factors that are associated with less weight loss, we have not found any factor that predicts an unacceptably low weight loss and thus provides a contraindication to Lap-Band® placement. The findings of this study allow us to set more realistic goals for the rate of weight loss in specified sub-groups of our patients.