Screening and Consent Prospective subjects who pass the initial phone screening interview (i.e. meet inclusion/exclusion criteria) will be admitted into the study and scheduled for a consent visit. At the consent visit, after singing the consent form and agreeing to participate, participants' weight, height, and blood pressure will be measured to ensure that they meet inclusion criteria, and if their measurements agree with their reported values they will be admitted into the study and scheduled for their baseline visit. At the consent visit, subjects will also be instructed on how to complete a 3-day food record and will be asked to complete and return it before the baseline visit. Participants will also be given a stool collection kit during the consent visit to collect stool samples within 24 hours before their first scheduled visit. Women who consent to participate will be scheduled to complete the study within the luteal phase and menses of the menstrual cycle to avoid confounding alterations in lipoproteins. If women participants are not able to remember the first day of their last menstrual cycle, they will be instructed to note the start of their next menstrual cycle and will then be scheduled accordingly thereafter. Subjects will be randomized to begin either on the fast food arm or the Med arm. Each cohort of 4 participants will have 2 individuals who begin on the Med diet arm, and 2 individuals who begin on the fast food diet arm, and each participant will be randomized into one of these two blocks and be assigned a study ID number.