Method: prospective study of 50 patients, aged over 18 years, with a body mass index above 30 kg/m2, urinary calculi and lithogenic metabolic abnormalities. Will be excluded from the study patients with psychiatric diagnoses other than depression, patients with inability to attend to clinical follow-up, patients with nephrocalcinosis, patients with urinary tract infection, patients with cystinuria and patients subjected to previous surgeries to treat obesity. Each patient will be evaluated monthly on the same day by urologist and nutritionist. On the first evaluation, will be done anamnesis, anthropometric measurements of weight, height, waist, bioimpedance and requested total serum calcium, phosphate, sodium, potassium, urea, creatinine, uric acid, and PTH, pH venous blood, urine tests type I, culture of urine and urine tests of calcium, oxalate, phosphate, sodium, potassium, citrate, magnesium, creatinine, uric acid, cystine and computed tomography for evaluation of urinary calculus. In the second evaluation, 30 days after, anthropometric measures will be repeated, bioimpedance and nutritional assessment will be made with recommendation of daily ingestion of 2500 ml of water and low-calorie diet of 16 Kcal/kg bw/day and requested total serum calcium, phosphate, sodium, potassium, urea, creatinine, uric acid, and PTH, pH venous blood, urine tests type I, culture of urine and urine tests of calcium, oxalate, phosphate, sodium, potassium, citrate, magnesium, creatinine, uric acid, cystine. Patients will be monitored monthly for 3 months with anthropometric measurements, bioimpedance and strengthening of nutritional recommendations. By the end of the third month, patients will be submitted to two series of serum and urine tests as before the diet. The results of serum and urine tests from the beginning of dietary treatment will be compared to those of the end of the treatment with Student T test. P<0.05 are considered significant.