Summary

Healthy individuals who gain weight are at risk of developing chronic kidney disease, even if they stay within the so-called normal weight range. The new findings come from annual health exams carried out on men in Korea. They show how those whose weight fluctuated the least had the lowest risk of kidney disease.

Introduction

Increasing numbers of people are developing end stage renal disease (ESRD) and it is preceded by a condition known as chronic kidney disease (CKD). If we could diagnose, and deal with, CKD at an early stage, then progression to ESRD could be slowed or even halted. We already know that obesity is a risk factor for both ESRD and CKD but not much is known of the risk, if any, associated with modest weight gain that still leaves the individual within a 'healthy' weight range. This study comes from Korea and refers to the World Health Organization's definition of BMI (body mass index) ranges for Asians. A healthy weight is BMI between 18.5 and 23, overweight from 23 to 25, and BMI over 25 is considered obese. Since the healthy range is quite wide, people may think it's OK to put on a bit of weight as they age, so long as their BMI doesn't go over 23.

What was done

Researchers at the Kangbuk Samsung Hospital in Seoul, took data - including BMI - from 8,792 healthy men undergoing a worksite health check in 2002 and followed up for the next few years. During this time, there were 427 new cases of CKD.

What was found

In both the normal weight and overweight groups, a U-shaped curve was found between weight change and risk of CKD. That is, minimal weight change was associated with lowest risk. Those who either lost or gained weight had a higher risk of CKD.

What this study means

This is the first study to show a link between weight gain within the normal range and the risk of CKD. Weight loss was linked with increased risk too, but the researchers believe this result needs to be treated with caution - the weight loss could be a symptom of ill health that itself contributes to CKD. They are not sure just why weight gain increases the risk of CKD - but it may be because of increases in body fat. We also know that weight gain increases the risk of hypertension (high blood pressure) and diabetes which can, in turn, increase the risk of kidney disease. But the current findings suggest that weight gain is an independent risk factor of kidney disease. The take-home message seems to be that it is important to keep your weight steady as you age if you want to avoid kidney disease and its complications.