Abstract
ABSTRACTPurpose:to evaluate the effect of low-calorie diet on 24-hour urinary metabolic parameters of obese adults with idiopathic calcium oxalate kidney stones.Materials and Methods:Adult idiopathic calcium oxalate stone formers, with body mass index (BMI) ≥30kg/m2 and a known lithogenic metabolic abnormality, were submitted to low-calorie diet for twelve weeks. After enrolment, anthropometric measures, serum exams, 24-hour urinary metabolic parameters and body impedance were collected one month prior to dietary intervention and at the end of twelve weeks. Correlations between weight loss, waist circumference loss, fat loss and variation in 24-hour urinary lithogenic parameters and calcium oxalate urinary supersaturation (CaOx SS) as per Tiselius equation were analysed.Results:From January 2017 to January 2018, 39 patients were enrolled to participate in this study. Median (range) prescribed diet was 1300 (1100-2100) Kcal/day. Mean age was 51.7±11.0 (29-68) years old and 69.2% were female. 30.8% of the participants shifted from obesity to BMI <30kg/m2 and none to BMI <25kg/m2. A significant correlation was found between baseline 24-hour urinary oxalate and weight (p=0.018) and BMI (p=0.026). No correlation was found between variation of weight, waist circumference, fat mass and 24-h urinary stone risk factors or CaOx SS.Conclusions:Short-term modest weight loss induced by twelve weeks of low-calorie diet is not associated with a decrease of 24-hour urinary lithogenic parameters in idiopathic calcium oxalate stone formers. Calcium oxalate urinary stone formation is probably multifactorial and driven by other factors than weight.
Highlights
Epidemiological evidence suggests that the increasing prevalence of kidney stone disease may be associated with the uprising prevalence of obesity
Spearman’s correlations between baseline 24-hour urinary lithogenic parameters and baseline weight, body mass index (BMI), waist circumference and body fat demonstrated a significant correlation between 24-hour urinary oxalate and weight (p=0.018) and BMI (p=0.026)
Previous studies have demonstrated that urolithiasis is more common among obese than normal weight individuals and that there is a correlation between increasing BMI and increasing stone risk factors [1, 7, 8, 19]
Summary
Epidemiological evidence suggests that the increasing prevalence of kidney stone disease may be associated with the uprising prevalence of obesity. Between 1988 and 2010, the prevalence of urolithiasis in the United States of America increased from 5.2% to 8.8% whereas the prevalence of obesity increased from 22.5% to 37.4% between 1988 and 2014 [1, 2]. It has been demonstrated that urolithiasis is more common among obese than normal weight individuals [1]. Weight loss is a well-established therapy to mitigate mortality and risk factors related to obesity. Intentional weight loss may be associated with approximately 15% reduction in all-cause mortality [3]. It is believed that a sustained reduction as modest as 3% to 5% of the body weight is already beneficial in order to reduce some of the risks associated to obesity [4]. Some comorbid conditions need a reduction of 10% to 15% to translate into clinical improvement [5]
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