Metabolomics Initiative: Mediterranean-amplified vs Habitual Western Diet on Food Signatures, Health, and Microbiome

The investigators propose to conduct a 16-week randomized, cross-over, semi-controlled feeding study of two isocaloric dietary interventions: 1. Mediterranean-amplified habitual/Western (mini-MED) diet, containing 500 kcal/day from Mediterranean target foods (such as raspberries, avocado, red bell pepper, basil, walnuts, chickpeas, oats, salmon); and 2. Habitual/Western (Western) diet, containing 500 kcal/day from non-Mediterranean target foods (such as potato, beef, sour cream, refined grain bread, chocolate dessert); among individuals who are not already consuming a Mediterranean-style dietary pattern. Participants will have overweight or obesity and meet criteria for Metabolic Syndrome (MetS), and therefore be at increased risk of cardiometabolic disease (CMD).

The primary goal is to validate results from metabolomics analyses of foods and biospecimens from a completed Mediterranean-style dietary intervention in a prospective feeding trial. Secondary aims are to evaluate impacts of incremental changes in diet on cardiometabolic health and microbiome structure/function. The primary hypothesis is that pre-defined metabolomics signatures in participant biospecimens will be responsive to dietary intakes and reproducible within individuals over time. The secondary hypotheses are that a Mediterranean-amplified diet will lead to improvements in cardiometabolic health and changes in microbiome structure/function over time and compared to a habitual Western diet.

Aim 1: Test reproducibility of pre-defined signatures from Mediterranean target foods provided in mini-MED in biospecimens (blood/urine) within individuals over time. Participants will complete a 16-week randomized cross-over dietary intervention of mini-MED vs Western diet. The investigators hypothesize that: (1) novel food-specific compounds will increase in participant biospecimens after consumption of mini-MED and decrease during Western diet, and (2) established biomarkers of fruit/vegetable intake (e.g., plasma and skin carotenoids, urine polyphenols) and other target foods (e.g., plasma alkylresorcinols, astaxanthin) will increase after consumption of mini-MED.

Aim 2: Determine the impact of mini-MED on cardiometabolic health. Cardiometabolic health indicators (e.g., blood pressure, lipid panel, inflammatory cytokines, indicators of subclinical inflammation) will be assessed pre- and post- each intervention. The investigators hypothesize that consumption of mini-MED will lead to improvements in cardiometabolic health indicators (e.g., reductions in blood pressure, total cholesterol, LDL cholesterol, triglycerides, C-reactive protein, bioactive lipids; increases in HDL cholesterol) over time and compared to Western diet.

Aim 3: Evaluate changes in microbiota community structure/function in response to mini-MED. Microbiome structure (taxonomy) and function (metagenomics) will be assessed pre- and post- each intervention. The investigators hypothesize that consumption of mini-MED will lead to increases in microbiome diversity and enrichment in taxa associated with increased production of health-promoting compounds (e.g., short chain fatty acids) over time and compared to Western diet.

Inclusion criteria

• Overweight or obesity (BMI 25-37 kg/m2) and weight-stable;
• Age 30-69 years;
• Nonsmoker (including tobacco, marijuana, and other inhaled substances);
• Consistent physical activity levels for 3 months prior to and throughout the study period;
• Stable medication use for 6 months prior to and throughout the study period;
• Having at least three components of Metabolic Syndrome (MetS): i.e., impaired fasting glucose, hypertension, central adiposity (waist circumference ≥ 94 cm or 80 cm, for men and women, respectively), fasting hypertriglyceridemia, and/or low levels of HDL cholesterol17 OR on medication for the treatment of hyperglycemia, hypertension, or hypercholesterolemia in lieu of meeting the corresponding MetS component;
• Report of baseline consumption of a habitual diet not meeting criteria for a Mediterranean-style dietary pattern, defined as a score of <5 as assessed via the Mediterranean Diet Assessment Tool
• Follows an omnivorous diet and willing to consume all provided foods (e.g., will eat salmon, fruits/vegetables, beef);
• Willingness to refrain from consumption of nutritional supplements, herbal supplements, botanical supplements, and pre- or probiotics aside from those prescribed by a physician for the duration of the study;
• Willingness to come to the CTRC biweekly for clinical assessments and biospecimen collection;
• No plans to relocate or for extended travel (>1 week) within next 6 months; and
• Capable and willing to provide informed consent

Exclusion criteria

• Use of medications contraindicating increased consumption of fruits/vegetables (e.g., warfarin);
• Diagnosis of acute or chronic condition impacting appetite, food intake, and/or the metabolism and absorption of foods to be provided (e.g., Crohn's disease, Celiac disease, Ulcerative colitis, short bowel syndrome, chronic diarrhea);
• Impaired liver or kidney function;
• Food allergies to foods provided in either dietary intervention;
• Vegetarian, vegan; and
• For females: pregnant or lactating or planning to become pregnant during study period