Kidney disease and obesity paradox

has been considered as one of important risk factors for cardiovascular (CV) disease and mortality in the general population. As its harmful aspect has been too much emphasized, many physicians ignore other facets of overweight/obesity nowadays. A number of epi-demiologic studies from large samples of chronic kidney disease (CKD) and end-stage renal disease (ESRD) have reported that worse survival was observed with a lower body mass index (BMI), and higher values of BMI reflecting overweight or obesity seemed to be associated with better survival. This phenomenon has been referred to obesity paradox [1]. It is universal phenomenon beyond regional and racial difference. In Korean patients with ESRD, BMI level was inversely associated with mortality and the association were very similar with Caucasians and African-Americans [2]. A recent nationwide cohort study in Korea also showed that subjects with a BMI of 25.0-29.9 kg/m 2 had a lower risk of mortality compared with the reference (BMI, 23-24.9 kg/m 2) in the elderly and patients with chronic diseases (diabetes mellitus, hypertension, and CKD) [3]. Of note, obesity paradox was not restricted to patients with CKD/ESRD but has been also observed in the elderly and in patients with other chronic diseases such as congestive heart failure and ma-lignancy. Obesity paradox may not necessarily mean that the principles of vascular pathology are different between a specific disease population and the general population. More dominant factors may overwhelm the traditional relation between obesity and worse outcomes as seen in the general population. Among several hypotheses, two points of view are worth bearing in mind [1]. The first is protein-energy wasting (PEW), which is a condition for simultaneous loss of systemic body protein and fat mass (energy reservoir) [4]. PEW may debilitate physiologic functions of the various organs and may affect clinical outcome in addition to a specific disease itself. In situation of deficiency or excessive consumption in energy, obesity may potentially attenuate the magnitude of PEW, resulting in favorable outcomes in patients. The second is time discrepancies among competing risks. Effects of obesity leading to cardio-metabolic derangement occur over a long period and have been reported from studies in long-living papulations. However, favorable effects of obesity on PEW may, in the short term, outweigh harmful effects on CV disease in the long term. Please note that mean or median follow-up durations were less than 5 years in most studies reporting obesity paradox from patients with ESRD …