Obesity linked to kidney stones

Obese people are more likely to develop kidney stones than normal weight individuals, but severe obesity doesn't seem to further increase the risk.

Kidney stones are solidified deposits of minerals and acid salts. Passing the small stones in the urine can be extremely painful. Surgery or other types of treatment may be required in some patients if they are unable to pass the stone on their own.
Studies have shown a rise in kidney stone disease paralleling the increase in obesity. It's unclear why weight would affect kidney stone rates, although researchers have a number of theories involving different levels of substances in the blood among the obese.

Researchers analysed the records for more than 95,598 people included in a national private insurance database. The researchers identified 3,257 people with kidney stones. Men were twice as likely as women to have kidney stones, while the risk of stones increased with age. They used the body mass index (BMI) - a standard measure used to gauge how fat or thin a person is - to classify patients' weight.

Among people classified as either normal weight ( BMI 18.5-24.9) or overweight (BMI 25-29.9 ) but not obese, about one in 40 had been diagnosed with kidney stones, compared to about one in 20 of those classified as obese (BMI above 30). But there was no significant difference in risk among severely obese (BMI above 35) individuals, no matter how heavy they were.

It was found that those who were obese were more likely than the non-obese to undergo kidney stone removal, but severely obese had the same risk as their normal weight peers. The researchers noted that it could be possible that the heaviest people were more likely to have their kidney stones treated with medication than surgery.

The findings show that obesity is associated with a higher risk of kidney stone disease.