NEW YORK (Reuters Health) – In healthy men of normal weight, relatively small increases in weight raise the risk of chronic kidney disease (CKD), according to a report by Korean researchers that will appear in the September issue of the Journal of the American Society of Nephrology.

The study, researchers say, suggests that CKD should be added to the list of conditions that are associated with weight gain, including diabetes and high blood pressure.

Obesity is a known risk factor for CKD, but the impact of weight gain in normal-weight individuals without high blood pressure or diabetes is unknown, Dr. Seungho Ryu, at Kangbuk Samsung Hospital in Seoul, and associates note in their report.

In Korea, workers are required to undergo periodic health examinations. Using these data, Ryu’s team followed 8792 healthy men ages 30 to 59 years with no known risk factors for CKD between 2002 and 2007. The prevalence of obesity was about 33 percent.

During followup, 427 men were diagnosed with CKD. Body mass index (BMI) categories at the start of the study (i.e., underweight, normal weight, overweight, obese) were not significantly associated with the development of CKD.

However, the researchers observed a U-shaped association between changes in weight categories among normal-weight and overweight subjects and the development of CKD.

Men who lost or gained a lot of weight (more than 0.75 kilograms, or 1.7 pounds, per year) had the highest risk of developing CKD. Increased risk was seen among men with even small weight changes. The lowest risk observed was among those who gained or lost as little as 0.25 kilograms, or 0.6 pounds, per year.

“Our findings show that weight gain within ‘the normal’ weight range is clearly one of the risk factors in developing CKD, and initial low body mass index does not counteract the deleterious effect of weight gain,” they conclude.

“Therefore, avoidance of weight gain, even among lean individuals, is important to reduce the risk for this disease.”

SOURCE: Journal of the American Society of Nephrology, September 2008.