NEW YORK (Reuters Health) – In healthy men of normal weight, relatively small weight gain can adversely affect glomerular filtration rate, an indicator 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.

A better understanding of risk factors for CKD is required to prevent end-stage renal disease, Dr. Seungho Ryu, at Kangbuk Samsung Hospital in Seoul, and associates note. Obesity is a known risk factor, but the influence of weight gain in normal-weight individuals without hypertension or diabetes is unknown.

In Korea, workers are required to undergo periodic health examinations. Using these data, Dr. Ryu’s team prospectively followed a cohort of 8792 healthy men ages 30 to 59 years with no known risk factors for CKD between 2002 and 2007. The prevalence of obesity was 33.4%. CKD was defined as an estimated glomerular filtration rate of < 64 mL/min per 1.73 m².

During nearly 36,000 person-years of follow-up, 427 incident cases of CKD were diagnosed. Baseline body mass index (BMI) categories (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. Increased risk was seen among subjects with even small weight changes. The lowest risk observed was among those who gained or lost no more than 0.25 kg/yr.

This association remained after adjustment for age and other factors at baseline, including glomerular filtration rate, BMI, HDL cholesterol, insulin resistance, incident hypertension and diabetes.

Dr. Ryu and associates point out that the increased risk associated with weight loss should be interpreted with caution, since they could not differentiate between intentional and unintentional weight loss.

“Our findings support that, even in a normal-weight population, a low initial BMI does not ameliorate the increase in risk for CKD with weight gain,” they conclude. “Therefore, avoidance of weight gain, even among lean individuals, is important to reduce the risk for this disease.”

J Am Soc Nephrol 2008.