Weighing the evidence: obesity, metabolic syndrome, and the risk of chronic kidney disease

Evaluating effect of obesity per se and the metabolic syndrome as a whole on the risk of developing chronic kidney disease (CKD) is key factor in developing a comprehensive public health approach to reduce morbidity and healthcare resource consumption. While there is considerable evidence to support increased risk of CKD in obese individuals and those with the metabolic syndrome, this relationship may be influenced by several factors. These include confounding variables, anthropometric measures, the end-point studied (e.g. development of early stage CKD, progression to end-stage renal disease or mortality), and the complex interrelationship between the various components of the metabolic syndrome. The study by Cao et al. in the current issue of BMC nephrology examines the impact of obesity on CKD risk in people with and without co-existing metabolic syndrome. The findings of this large, prospective study illustrate a clear correlation between increased body mass index (BMI) and risk of CKD regardless of whether or not there is co-existing metabolic syndrome. While the presence of the metabolic syndrome confers some additional risk of CKD in overweight and obese individuals, its effect is relatively modest and accounts for only 26 % of the risk associated with increased BMI. We discuss the complex epidemiological and methodological context in which these important findings should be understood, and their implications for public health and for individual patients and healthcare practitioners.