Weight Loss and Proteinuria

Obesity is a risk factor for the progression of chronic kidney disease (CKD). This study aimed to determine the effect of intentional weight loss on proteinuria and kidney function….

Three bibliographic databases including Medline, Cochrane and SCUPOS, as well as reference lists of articles were searched. Randomized and non-randomized controlled trials were included as well as single-arm trials published in English through May 2009 which examined urinary protein among obese or overweight adults before and after weight loss interventions including dietary restriction, exercise, anti-obesity medications and bariatric surgery. Study characteristics and methodological quality of trials were assessed.

Five hundred twenty-two subjects from five controlled and eight uncontrolled trials were included. Weight loss interventions were associated with decreased proteinuria and microalbuminuria by 1.7 g and 14 mg, respectively (P < 0.05). Meta-regression showed that, independent of decline in mean arterial pressure, each 1 kg weight loss was associated with 110 mg (P < 0.001) decrease in proteinuria and 1.1 mg (P = 0.011) decrease in microalbuminuria, respectively. The decrease was observed across different designs and methods of weight loss. Only bariatric surgery resulted in a significant decrease in creatinine clearance.

The results showed a decline in urinary protein excretion is associated with a significant decrease in cardiovascular risks and events. Therefore, albuminuria is not only a surrogate marker of increased mortality and morbidity but also viewed as a therapeutic target and, therefore, any attempt for its decline may have beneficial effects. Unintentional weight loss as observed in advanced stages of chronic illnesses such as end-stage kidney diseases, advanced heart failure or old age may be a reflection of cachexia-inflammatory status of the chronic illness and often is highly associated with mortality. However, the increased mortality in such entities are often reported through observational studies which have not been able to distinguish intentional from unintentional weight loss or ignored adequate adjustments by chronicity or severity of underlying illnesses, sending controversial messages about the benefits of intentional weight loss. The patients in trials of this review are also categorized as mild to moderate kidney failure without heart failure.

From the results it was concluded that weight loss is associated with decreased proteinuria and microalbuminuria. There were no data evaluating the durability of this decrease or the effect of weight loss on CKD progression. The evidence supports the beneficiary effect of weight loss on the surrogate outcomes of the decrease of urinary protein excretion. Further research is required to determine the impact of weight loss on clinical renal outcomes.

Nephrol Dial Transplant. 2010;25(4):1173-1183