Mediterranean-like Unprocessed (CLEAN-MED) Diet Intervention Study of the Gut Microbiome of Healthy Adults

* INCLUSION CRITERIA: In order to be eligible to participate in this study, an individual must meet all of the following criteria: * Ability of subject to understand and the willingness to sign a written informed consent document * Age 18-60, at the time of consent * Willingness to adhere to the dietary regimen and report any major stressors that occur during the study (i.e. changing jobs, moving, death of a close relative/friend, etc.) * Willingness to provide blood and stool specimens as specified * BMI \>=18 and \<= 35 kg/m\^2 * Access to necessary resources for participating in a technology-based intervention: computer, smartphone, internet access, etc. * Has the ability/transportation methods to attend on-site visits * For 50 of the 60 participants in short-term cohort and for 40 of the 50 participants in the long-term cohort: Currently following a Western diet with PREDIMED-17 MedDiet score \<= 7 for \>= 1 months and a CLEAN-MED NOVA score of \>= 35% kcal in NOVA 4 category with \>= 14 items/week in NOVA 4 * For 10 of the 60 participants in short-term cohort and for 10 of the 50 participants in the long-term cohort: Currently following a Western diet with PREDIMED-17 MedDiet score \<= 10 for \>= 1 months and a CLEAN-MED NOVA score of \>= 20% kcal in NOVA 4 category with \>= 7 items/week in NOVA 4 * CLEAN-MED Logging Score of \>= 43 after initial trial week to continue in the study for the randomization step * For long-term cohort only: Have resources and capability to consume freshly-cooked (i.e. not pre-packaged or frozen) meals EXCLUSION CRITERIA: An individual who meets any of the following criteria will be excluded from participation in this study, at the discretion of the PI: * Current use of medications or dietary supplements for weight or appetite control, whether prescribed or not, including laxatives (within the last 4 weeks) * Currently eating a vegan, vegetarian, keto or other restrictive diet plan, or food allergies that would affect eating the study diet, at the discretion of the PI * Active cardiovascular disease (in past year with myocardial infarction, coronary stent or bypass surgery) * Diabetes (type 1 and 2) or history of gestational diabetes or on hypoglycemic medications or any other indication * Kidney disease (eGFR less than 50 mL/min per 1.73 m\^2) * Liver disease (liver transaminase higher than 3 times the normal range for the laboratory) * Symptomatic gallstones * History of active cancer in the past 3 years except for squamous or basal cell carcinomas of the skin that have been medically managed by local excision * Has a diagnosed autoimmune condition (i.e. HIV, lupus, etc.) or other immunosuppressive or immunodeficient state, at the discretion of the PI * Musculoskeletal disorders precluding regular physical activity * Consumption of the following drugs: proton pump inhibitors, antidiabetic drugs, cholesterol lowering drugs, SGLT-2 inhibitors, GLP-1 receptor agonist, insulin, Amylin analog, Alpha-glucosidase inhibitor, Dopamine agonist, Bile acid sequestrant, corticosteroids, methotrexate or immunosuppressive cytotoxic agents * Some types of abdominal surgery, including bariatric surgery, or severe intestinal problems (by discretion of study physician), including: * Inflammatory bowel disease (IBD) including ulcerative colitis (mild-moderate-severe), Crohn s disease (mild-moderate-severe), or indeterminate colitis; * Irritable bowel syndrome (IBS) (moderate-severe); * Persistent, infectious gastroenteritis, colitis or gastritis, persistent or chronic diarrhea of unknown etiology, Clostridium difficile infection (recurrent) or Helicobacter pylori infection (untreated); * Chronic constipation * Consumes more than 3 alcoholic beverages per day * Currently receiving or has received antibiotics, antifungals, antivirals, or antiparasitics in past 2 months * Is currently using or has used probiotic supplements within the last 2 months * Is currently on a weight-loss program or has experienced a weight change (gain or loss) of greater than 15 pounds in the past 3 months * Has a history of hospitalization for mental health condition and/or has had a change in depression or anxiety prescription medications within the past 10 weeks (by discretion of study physician) * Is pregnant or breastfeeding or planning pregnancy within the time of the study * Subjects who are not fluent in English * Use of smoking or chewing tobacco, e-cigarettes, cigars, or other nicotine-containing products, or cannabis * Regular use of prescription opiate pain medication * Weight \<100 lbs * Acute disease, defined as the presence of a moderate or severe illness with or without fever, at the time of enrollment * Inability to communicate effectively with study personnel * Lack of commitment with the intervention or non-compliance (at the discretion of the investigator) * Eating disorders