Obesity is a growing health issue that effects the majority of adults in the United States. Prevalence of other metabolic diseases are increased in obese adults, including systemic inflammation. There is emerging evidence that the gut microbiota have a mediating role in controlling inflammation by producing butyrate when ingested fiber is fermented. Since these microbes are modifiable by diet, the investigators plan to introduce walnuts to the diets of participants with obesity because they are rich in fiber and unsaturated fatty acids. The purpose of this study is to understand the impacts of walnut consumption on the gut microbiota and the effect they have on bile acid profiles and systemic inflammation. The investigators intention is to identify how these walnut-derived molecules influence Faecalibacterium spp., a butyrate producing microbe. Increased levels of butyrate have shown to decrease secondary bile acids and decrease inflammation.

Inclusion Criteria:

Participants will include adults ages 25-75 years BMI of > 30 kg/m2 Ability to drop-off fecal sample within 15 minutes of defecation

Exclusion Criteria:

• Walnut allergy or intolerance
• Food allergies or intolerances
• Prior diagnosis of metabolic or gastrointestinal disease (cardiovascular disease and type 1 or type 2 diabetes, chronic constipation, diarrhea, Crohn's disease, celiac disease, ulcerative colitis, irritable bowel syndrome, diverticulosis, stomach or duodenal ulcers, hepatitis, HIV, cancer, etc.)
• Women that are pregnant, had a baby within the last 12 months, or lactating
• Individuals that smoke, use tobacco, abuse drugs, or consume > 2 alcoholic beverages per day.
• > 5% weight change in the past month or > 10% change in the past year
• Oral antibiotics during the previous 6 weeks
• Fasting blood glucose >126 mg/dL, blood pressure >160/100 mm Hg, elevation in serum transaminases (i.e. >3 times the upper limit of normal) or with evidence of liver disease, including primary biliary cirrhosis or gallbladder disease, constipation, are currently taking lipid-lowering medications, oral hypoglycemic agents, or insulin, or certain medications (laxatives, bile acid sequestrants, and opiates)
• History of malabsorptive or restrictive bariatric surgeries (e.g., gastric bypass, sleeve gastrectomy, adjustable gastric band) or gall bladder removal surgery.
• Are unable to consume the experimental meals/snacks.
• Participants who have donated blood within the last 8 weeks
• Recent diagnosis of anemia
• Concurrent enrollment in another dietary, exercise, or medication study