Study Arm 2: (4 days) At this time, participants who completed the mMed diet arm will now begin the fast food diet arm, and those who completed the fast food diet arm will now enter the mMed diet arm. All participants will be asked to complete a hunger and satiety questionnaire during this time (4 days). At the end of the 4-day period subjects will return for the third follow-up study visit (Study Visit D). Participants will be required to collect a final stool sample to bring with them to their visit.