BACKGROUND: To compare implantable gastric stimulation therapy with a standard diet and behavioral therapy regimen in a group of carefully selected class 2 and 3 obese subjects by evaluating the difference in the percentage of excess weight loss (EWL) between the control and treatment groups. The primary endpoint was the percentage of EWL from baseline to 12 months after randomization. Implantable gastric stimulation has been proposed as a first-line treatment for severely obese patients; however, previous investigations have reported inconclusive results. METHODS: A total of 190 subjects were enrolled in this prospective, randomized, placebo-controlled, double-blind, multicenter study. All patients underwent implantation with the implantable gastric stimulator and were randomized to 1 of 2 treatment groups: the control group (stimulation off) or treatment group (stimulation on). The patients were evaluated on a monthly basis. All individuals who enrolled in this study agreed to consume a diet with a 500-kcal/d deficit and to participate in monthly support group meetings. RESULTS: The procedure resulted in no deaths and a low complication rate. The primary endpoint of a difference in weight loss between the treatment and control groups was not met. The control group lost 11.7% +/- 16.9% of excess weight and the treatment group lost 11.8% +/- 17.6% (P = .717) according to an intent-to-treat analysis. CONCLUSION: Implantable gastric stimulation as a surgical option for the treatment of morbid obesity is a less complex procedure than current bariatric operations. However, the results of the present study do not support its application. Additional research is indicated to understand the physiology and potential benefits of this therapy.