Brain Response to Dietary Interventions

Participants will be provided instruction in the appropriate use of the meal replacement product. The participants will be directed to refrain from all items of food for a period of 21 days except for the meal replacement products and vitamin supplements provided by the investigators (1120 kcal/day). Optifast™ 800 total meal replacement shakes will be provided to the participants for the 21 day intervention period.

Participants will be directed to use portion control to maintain a calorie level no greater than 1120 kcal per day. The participants will be directed to continue to consume food and beverage items that are representative of their typical diet (with the exception of reduced portions). Participants will be provided resources to assist them in determining caloric content of foods eaten.