Obesity in renal failure--health or disease?

Abstract

The results of numerous investigations on the impact of obesity on renal insufficiency conducted in recent years introduce certain dilemmas about their mutual agreement. Some studies suggest that obesity is negatively correlated with the terminal phase of renal failure. On the other hand, other research has shown that reducing the index of body weight of patients with renal disease improves glomerular filtration. Even more confusion comes from findings indicating that metabolic syndrome in non-diabetic renal disease sufferers increases the risk of occurrence and progression of chronic renal disease. However, some research results suggest that obesity is positively correlated with survival of patients on dialysis, i.e., the higher the index of body weight the lower the mortality rate, especially with extremely obese patients. Reverse epidemiology is a term for the medical hypothesis which holds that the influence of obesity and high body weight indexes may be protective and associated with greater survival of obese patients on haemodialysis. A high serum creatinine concentration is a direct consequence of low rates of glomerular filtration and is inversely correlated with mortality rate. However, observations that high creatinine concentrations before haemodialysis treatment are a predictor of survival may be explained by the fact that they are also the direct consequence of increased muscle mass and a higher dietary protein intake. Thus, improvement of their nutritive state might delay progression and diminish the complications expected for patients suffering from kidney insufficiency. The requirements for daily protein intake by dialysis patients are not clear enough, while a hyperprotein diet may be a significant source of uraemic toxins, phosphate and H(+)-ion, which would be detrimental for their health. Some research has indicated that obesity of dialysis patients is not linked to increased risk of cardiovascular diseases in contrast to the general population. On the other hand, a low body mass index and additional parameters of malnutrition are strong independent indicators of mortality rate in dialysis patients. Although, there is a substantial amount of data that support a protective role for obesity, some authors question the existence of the obesity paradox. They do not oppose the results of that research, but suggest that obese individuals are actually protected in the short-term while later on they are liable to higher mortality risks than people of normal body weight. The role of obesity is undisputed as a significant mortality factor in the general population. Nevertheless, some well-designed studies have confirmed that obesity has a protective influence on patients treated by chronic dialysis procedures. This is not to suggest that obesity is recommended as a model for a higher survival rate in those patients, but the role of 'uraemic adipose tissue' and probable additional factors that might result in a lower mortality rate should be considered.