The purpose of this feasibility study is to provide safety data on the implantable Exilis gastric electrical stimulation (GES) system, to individually adjust stimulation parameters to levels that are comfortable for implanted subjects during chronic daily treatment, and to collect data on acute gastrointestinal function and food intake responses to GES during in-clinic testing.

Inclusion Criteria:

• Adults ages 21-64 with BMI of 40-45 kg/m^2 or BMI 35-39.9 kg/m^2 with at least one obesity-related comorbidity, who have failed prior non-surgical weight loss attempts, and have been within 5% of their current weight for at least one year.
• If diabetic, subject has non-insulin-dependent type 2 diabetes mellitus diagnosed within the last 7 years, and has an HbA1c level less than 8%.
• If female and of child-bearing age, subject is not pregnant or lactating and is willing to use effective contraception for the duration of the study.
• Subject is willing and able to complete scheduled study visits, complete on-line lifestyle educational modules, and complete required procedures.

Exclusion Criteria:

• Subject has a history of medical, surgical, or psychiatric conditions that, in the opinion of the Investigators, would limit study participation or contraindicate implantation of the Exilis GES system. Examples includes cardiac abnormalities contraindicating surgical anesthesia, prior gastrointestinal surgery, gastrointestinal motility disorders, inflammatory bowel disease, a history of eating disorders, anticipated future need for magnetic resonance imaging, or allergies to food ingredients in study test meals.