Link Between Obesity and Residual Renal Function After Start of Dialysis

The Americal Journal of Kidney Disease (AJKD) is publishing a study in its June 2009 issue in regards to BMI (body mass index) and residual renal function on CKD5 patients starting on hemodialysis.

Although we know that obesity is a risk factor for progressive renal disease leading to end stage... does a high BMI impact residual renal function once a patients starts dialysis?

Apparently, so. A study of 1,271 incident dialysis patients from 38 centers in The Netherlands participating in the Netherlands Cooperative Study on the Adequacy of Dialysis (NECOSAD) between 1997 and 2006 was used to evaluate this question.

BMI assessed at 3 months after the initiation of dialysis therapy (baseline) and categorized into 4 groups: less than 20, 20 or greater to 25, 25 or greater to 30, and 30 or greater (25-29.9 = overweight; 30+ obesity).

The study wound up showing that in fact, obesity was a strong risk factor for the decline in kidney function after initiation of dialysis therapy. Whether obese dialysis patients might benefit from a healthy weight reduction needs to be studied further.

There aren't too many study showing that obesity is a good and protective state, so this is not surprising. We also know that obesity leads to worsening GFR over time... so it shouldn't be too surprising that the residual renal function will also fall quicker than in someone with a lower BMI. Nevertheless, it is a relatively small study done in the Netherlands which may not fully apply to Americans. The study also did not include BMI at the initiation of dialysis. They started collecting data 3 months after dialysis started. It is also unclear if lowering the BMI will preserve renal function once on dialysis. But, for now it seems safe (and logical) to continue to aim for an ideal BMI of 20-25.