The purpose of this study is to compare the efficacy (in terms of weight and hemoglobin type A1c [HbA1c]) and safety of topiramate (96 milligrams[mg] or 192 mg daily) with placebo in the treatment of obesity in Type 2 diabetic patients receiving metformin.

Topiramate is not approved for the treatment of obesity. This double-blind, placebo-controlled study is designed to assess the efficacy and safety of topiramate in Type 2 diabetic patients with obesity who are well-controlled on metformin alone. Patients are randomized to receive either topiramate (up to a target dose of 96 or 192 mg per day) or placebo for one year. Assessments of efficacy include weight reduction, levels of HbA1c (shows average blood sugar level over a few months), Body Mass Index (BMI), and Health Related Quality of Life (HRQOL) measures. Safety evaluations (incidence of adverse events, vital signs, hypoglycemic events, electrocardiograms [ECGs], clinical laboratory values) are monitored throughout the study. The study hypothesis is that topiramate, combined with metformin and non-pharmacologic therapy, can effectively achieve significant weight reduction and is well tolerated. During the first 8 weeks, oral doses of matching placebo or topiramate are increased gradually to target dose (96 milligrams[mg] or 192mg daily); the dose will be maintained for 1 year, then gradually reduced and stopped

Inclusion Criteria:

• Diagnosis of Type 2 diabetes and receiving metformin monotherapy for at least the previous 4 months and on a stable daily dose for at least 2 months prior to enrollment
• Metformin total daily dose not to exceed 2.1 grams/day
• Body Mass Index >= 27 and < 50
• HbA1c < 11%
• Fasting plasma glucose >= 126 and < 240
• Stable weight
• Female patients must be postmenopausal for at least 1 year, surgically incapable of childbearing, or practicing an acceptable method of contraception (requires negative pregnancy test)

Exclusion Criteria:

• Known contraindication, or hypersensitivity to topiramate
• Use of other antidiabetic medications within the last 4 months
• Excessive weight loss
• Diagnosis of type 1 diabetes
• History of severe or recurrent hypoglycemic episodes
• Severe pulmonary disease