Healthy individuals who gain weight, even to a weight still considered normal, are at risk for developing chronic kidney disease (CKD), according to a study appearing in the September 2008 issue of the Journal of the American Society Nephrology (JASN). The study suggests that CKD should be added to the list of conditions that are associated with weight gain, including diabetes and hypertension.

Research has shown that obesity is linked to an increased risk of CKD, but no studies have looked at the effects of weight gain within the "normal" range of an individual's body mass index. To investigate, Drs. Seungho Ryu and Yoosoo Chang of the Kangbuk Samsung Hospital in Seoul, Korea, and their colleagues conducted a prospective study of individuals who were of a healthy weight and had no known risk factors for chronic kidney disease.

In Korea, all workers participate in either annual or biennial health exams, as required by Korea's Industrial Safety and Health Law. As a result, the investigators had access to clinical data from thousands of individuals. For this study, they included 8,792 healthy men who participated in the health exams in 2002.

The researchers discovered a U-shaped association between weight change and development of CKD. Men who lost or gained a lot of weight (more than 0.75 kg per year) had the highest risk of developing CKD. Those whose weight changed minimally (within a range of -0.25 to