This study is testing the effects on weight loss of a capsule-delivered device that expands in the stomach to help create a sense of fullness. The device then leaves the stomach, disintegrates and is excreted. In this study participants will receive either the device or a placebo capsule that looks the same. Participants will receive dietary and exercise counseling at most visits to help them lose weight. The 24-week losses of participants who get the device will be compared to the losses of those who get the placebo capsule to determine the effect on weight loss. Changes in other health markers will also be assessed.