Influence of Obesity on Oxalate Metabolism and Handling in Calcium Oxalate Stone Formers

Inclusion Criteria: * Normal Body Mass Index (≥ 18.5 to \< 25); Obese Body Mass Index (≥ 30 to ≤ 45) * Able to provide informed consent * Willingness to consume controlled diet * Composition of most recent stone \> 50% calcium oxalate, no uric acid component * First time or recurrent calcium oxalate stone former * 24-hour urine collections with creatinine values within 20% of appropriate ratio of creatinine (mg)/body weight (kg) for gender, and with creatinine values that are consistent between collections (within 20% of each other) * Willingness to stop supplements \[vitamins, Ca (citrate or carbonate) and other minerals, herbal supplements, nutritional aids, probiotics\] for 14 days before start and during study * Willingness to not undertake vigorous exercise during the controlled dietary study * Normal fasting blood Comprehensive Metabolic Panel * Hemoglobin A1c \< 6.5% * No food allergies or intolerance to any of the food in study menus * Permitted/willing to discontinue medications for kidney stone prevention, including thiazides, allopurinol, and febuxostat and citrate preparations, for 14 days before start and during the studies. They will be instructed to restart these medications at the conclusion of the study Exclusion Criteria: * Diabetes * Abnormal fasting comprehensive metabolic panel (CMP) * Hemoglobin A1c (HbA1c) result ≥ 6.5% * Gout * Estimated Glomerular Filtration Rate (eGFR) \<60 ml/min/1.73m\^2 * Primary hyperoxaluria * Cystic fibrosis * Cystinuria * U…