There exists in the general population a complex and mostly positive relationship between adiposity and mortality risk. Because the dialysis population has a high prevalence of excess adiposity, in addition to a strikingly elevated mortality rate, the effects of obesity are of potential clinical importance. In contrast to the general population, the preponderance of data in dialysis, particularly hemodialysis patients, suggest that adiposity has a neutral or even protective association with mortality. Although methodological concerns exist with regards to confounding and survival bias, among others, the major limitation of this body of literature is its inability to establish causality. Thus, although obese dialysis patients, with certain exceptions, appear to live longer, there is no evidence to suggest that intentional weight loss adversely affects patient outcomes. In light of these limitations and the substantial body of literature implicating obesity as a pathophysiological state, it is currently premature to advocate for excess adiposity as being beneficial or intentional weight loss as dangerous. Decisions regarding optimal weight should be made by clinicians on an individual basis and with close supervision and follow-up. Efforts should be made to preserve lean mass during weight loss regimens by encouraging exercise and recommending sufficient protein consumption. Future research efforts in this area should focus on interventional trials designed to manipulate weight and measure outcomes, identifying potentially beneficial secretory products of adipose tissue, and documenting obesity's effects on quality of life and resource utilization in the dialysis setting.