Activity, energy intake, obesity, and the risk of incident kidney stones in postmenopausal women, "Beyond the Abstract," by Ryan Hsi, MD, and Mathew Sorensen, MD, MS

BERKELEY, CA ( - Kidney stones will affect 1 in 11 Americans, and the prevalence is rising. This trend has been attributed to the increasing rates of obesity, metabolic syndrome, and higher body mass index (BMI), which are known risk factors of kidney stones. Therefore the identification of modifiable dietary and lifestyle factors that decrease the risk of kidney stone formation has gained increasing attention.

An analysis of the data from the Women’s Health Initiative (WHI) Observational study published in the Journal of the American Society of Nephrology reported that postmenopausal women who are more physically active reduce their risk of developing kidney stones. The women who were more physically active in this study reduced the risk of incident kidney stones by up to 31% in adjusted analysis compared to women who performed no physical activity. More important than the intensity of exercise was the total amount of activity performed. This risk reduction was seen even with small amounts of exercise and increased up to 10 metabolic equivalents (METs) per week. This upper limit is approximately equal to 3 hours of walking or 1 hour of moderate jogging each week.

The study also reported an association between higher dietary intake of calories (more than 2200 kcal per day) and an increased risk of incident kidney stones. This association was seen even when adjusting for known dietary factors associated with stone formation, including water, sodium, animal protein, and calcium intake. As expected, women with higher BMIs had a greater risk developing kidney stones with a 31% adjusted higher risk in the severely obese (BMI 35 or greater) compared to women with normal BMI. An interesting finding was that women with the lowest caloric intake (less than 1800 kcal per day) did not have a decreased risk of stones in adjusted analysis.

Performing more exercise to prevent kidney stones adds to the growing list of benefits from exercise. It is well known that physical activity reduces the risk of obesity, type 2 diabetes, certain cancers, and cardiovascular disease. Exercise also protects against metabolic syndrome, which has been associated with the development of chronic kidney disease.

This is the first study to independently assess the effect of physical activity and caloric intake on the development of kidney stones. There are several possible theories for why exercise might affect kidney stone formation. Exercise stimulates thirst, leading to fluid intake in excess of what is lost during exercise, which might protect against stone formation. Physical activity also changes the way our bodies handle electrolytes and minerals important to stone formation. There is less sodium excretion with increased exercise, and if the activity is weight bearing, may encourage calcium to move into the bone rather than being excreted in the urine. Exercise also increases high-density lipoprotein (HDL) cholesterol and this might protect against dyslipidemia and the accompanying risk of stones. It is also possible that women who regularly exercise are decreasing their risk of metabolic syndrome, obesity, hypertension, and diabetes and this is leading to decreased stone formation. Lastly, it is possible that women who exercise are implementing other healthy dietary or lifestyle interventions that reduce the risk of stones.

While this study was limited to postmenopausal women, further studies are needed to confirm these findings in other populations. In addition, this study specifically examined women who had no prior history of kidney stones, and the findings may vary in those with recurrent stones.

Written by:
Ryan Hsi, MD, and Mathew Sorensen, MD, MS as part of Beyond the Abstract on This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.

University of Washington School of Medicine, Seattle, WA USA

Activity, energy intake, obesity, and the risk of incident kidney stones in postmenopausal women: A report from the Women's Health Initiative - Abstract

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