Obesity, Weight Gain, and the Risk of Kidney Stones

Abstract

Context Larger body size may result in increased urinary excretion of calcium, oxalate, and uric acid, thereby increasing the risk for calcium-containing kidney stones. It is unclear if obesity increases the risk of stone formation, and it is not known if weight gain influences risk.Objective To determine if weight, weight gain, body mass index (BMI), and waist circumference are associated with kidney stone formation. Design, Setting, and ParticipantsA prospective study of 3 large cohorts: the Health Professionals Follow-up Study (N=45988 men; age range at baseline, 40-75 years), the Nurses' Health Study I (N=93758 older women; age range at baseline, 34-59 years), and the Nurses' Health Study II (N=101877 younger women; age range at baseline, 27-44 years).Main Outcome Measures Incidence of symptomatic kidney stones. ResultsWe documented 4827 incident kidney stones over a combined 46 years of follow-up. After adjusting for age, dietary factors, fluid intake, and thiazide use, the relative risk (RR) for stone formation in men weighing more than 220 lb (100.0 kg) vs men less than 150 lb (68.2 kg) was 1.44 (95% confidence interval [CI], 1.11-1.86; P=.002 for trend). In older and younger women, RRs for these weight categories were 1.89 (95% CI, 1.52-2.36; PϽ.001 for trend) and 1.92 (95% CI, 1.59-2.31; PϽ.001 for trend), respectively. The RR in men who gained more than 35 lb (15.9 kg) since age 21 years vs men whose weight did not change was 1.39 (95% CI, 1.14-1.70; P=.001 for trend). Corresponding RRs for the same categories of weight gain since age 18 years in older and younger women were 1.70 (95% CI, 1.40-2.05; PϽ.001 for trend) and 1.82 (95% CI, 1.50-2.21; PϽ.001 for trend). Body mass index was associated with the risk of kidney stone formation: the RR for men with a BMI of 30 or greater vs those with a BMI of 21 to 22.9 was 1.33 (95% CI, 1.08-1.63; PϽ.001 for trend). Corresponding RRs for the same categories of BMI in older and younger women were 1.90 (95% CI, 1.61-2.25; PϽ.001 for trend) and 2.09 (95% CI, 1.77-2.48; PϽ.001 for trend). Waist circumference was also positively associated with risk in men (P=.002 for trend) and in older and younger women (PϽ.001 for trend for both). ConclusionsObesity and weight gain increase the risk of kidney stone formation. The magnitude of the increased risk may be greater in women than in men.

Muscularity and adiposity in addition to net acid excretion as predictors of 24-h urinary pH in young adults and elderly

“…A corresponding inverse relationship between adiposity indices (BMI or weight) and urinary pH has been suggested for patients especially with kidney stones (Maalouf et al, 2004;Siener et al, 2004), but not yet for healthy subjects. Whether lower urinary pH values in more obese subjects represent one mechanism explaining their increased risk for urolithiasis (Curhan et al, 1998;Siener et al, 2004;Taylor et al, 2005b) and whether insulin resistance is involved (Taylor et al, 2005a), is currently under discussion and needs further research. Protein intake is a known confounder of urinary creatinine excretion (Gibson, 1990;Neubert and Remer, 1998) and therefore has to be controlled for, if creatinine's specific muscularity contribution is to be investigated.…”

“…However, whether an NAE-adjusted 24-h urinary pH does actually correlate with adiposity can only be proved if biochemically analyzed NAE is used instead of excretion parameters as sulfate because a high protein intake and consequently high sulfate excretion does not automatically result in a high NAE (Sebastian et al, 2002;. In principle, an independent role of obesity in influencing the 24h-UpH may be of pathophysiological importance as the increased prevalence of kidney stones in obese subjects (Curhan et al, 1998;Borghi et al, 1999;Siener et al, 2004;Taylor et al, 2005b) could have been caused at least partly by an obesityrelated urine pH decrease (Maalouf et al, 2004). Kidney stones, especially idiopathic uric acid nephrolithiasis (Maalouf et al, 2004;Alvarez-Nemegyei et al, 2005), are usually associated with low urine pHs.…”

Obesity and kidney disease: hidden consequences of the epidemic

“…The deleterious effect of obesity on the kidneys extends to other complications such as nephrolithiasis and kidney malignancies. Higher BMI is associated with an increased prevalence 25 and incidence 26,27 of nephrolithiasis. Furthermore, weight gain over time, and higher baseline WC were also associated with higher incidence of nephrolithiasis 27 .…”

“…Higher BMI is associated with an increased prevalence 25 and incidence 26,27 of nephrolithiasis. Furthermore, weight gain over time, and higher baseline WC were also associated with higher incidence of nephrolithiasis 27 . Obesity is associated with various types of malignancies, particularly cancers of the kidneys.…”

Obesity and kidney disease: hidden consequences of the epidemic

“…Higher BMI is associated with an increased prevalence [25] and incidence [26,27] of nephrolithiasis. Furthermore, weight gain over time, and higher baseline WC were also associated with higher incidence of nephrolithiasis [27]. Obesity is associated with various types of malignancies, particularly cancers of the kidneys.…”