Effect of being overweight on stone-forming risk factors.

Objectives: To evaluate the possible role of being overweight on stone-forming risk factors.

Methods: A total of 264 patients were included in the study. After a detailed stone disease history, the systolic and diastolic blood pressure was precisely measured and recorded for all patients, and the body mass index, 24-hour urine composition, and serum stone-forming risk parameters were evaluated in overweight (n = 164; 52 men and 112 women; group 1) and normal (n = 100; 44 men and 56 women, group 2) patients. Of the 264 patients, 110 were men and 154 were women (male/female ratio 1:1.4); none had undergone any medical or dietetic treatment before study entry.

Results: The evaluation of the stone-forming risk factors in both groups revealed that obesity increased the excretion of these substances in group 1. Of the 164 patients in group 1, most (58; 35.3%) demonstrated hyperoxaluria compared with group 2 (P <0.001). Also, the mean urinary oxalate level was 44.91 +/- 24.89 mg/24 hours in group 1 and was 26.67 +/- 24.59 mg/24 hours in group 2 (P <0.001). Similarly, patients in group 1 had elevated mean urinary calcium excretion and lower citrate excretion compared with those in group 2 (P = 0.045 and P = 0.032, respectively).

Conclusions: Our results have clearly shown that being overweight might be associated with an elevated risk of stone formation in both sexes owing to alterations in urine composition. People who are overweight could be more prone to stone formation and should be carefully evaluated and followed up regarding this aspect.