Obesity and Kidney Disease: Hidden Consequences of the Epidemic

Abstract

IntroductionIn 2014, over 600 million adults worldwide, 18 years and older, were obese. Obesity is a potent risk factor for the development of kidney disease. It increases the risk of developing major risk factors for Chronic Kidney Disease (CKD), like diabetes and hypertension, and it has a direct impact on the development of CKD and end-stage renal disease (ESRD). In individuals affected by obesity, a (likely) compensatory mechanism of hyperfiltration occurs to meet the heightened metabolic demands of the increased body weight. The increase in intraglomerular pressure can damage the kidney structure and raise the risk of developing CKD in the long-term.The good news is that obesity, as well as the related CKD, are largely preventable. Education and awareness of the risks of obesity and a healthy lifestyle, including proper nutrition and exercise, can dramatically help in preventing obesity and kidney disease. This article reviews the association of obesity with kidney disease on the occasion of the 2017 World Kidney Day.Epidemiology of obesity in adults and childrenOver the last 3 decades, the prevalence of overweight and obese adults (BMI >25 kg/m2) worldwide has increased substantially.(Forouzanfar et al. 2287-323) In the US, the age-adjusted prevalence of obesity in 20132014 was 35% among men and 40.4% among women.(Flegal et al. 2284-91) The problem of obesity also affects children. In the US in 2011-2014, the prevalence of obesity was 17% and extreme obesity 5.8% among youth 219 years of age. The rise in obesity prevalence is also a worldwide concern,(Cattaneo et al. 389-98;Olaya et al. 475) as it is projected to grow by 40% across the globe in the next decade. Low- and middle-income countries are now showing evidence of transitioning from normal weight to overweight and obesity as parts of Europe and the United States did decades ago.(Subramanian et al. 413-21) This increasing prevalence of obesity has implications for cardiovascular disease (CVD) and also for CKD. A high body mass index (BMI) is one of the strongest risk factors for new-onset CKD.(Tsujimoto et al. 444-51;Elsayed et al. 29-38)Definitions of obesity are most often based on BMI (i.e. weight [kilograms] divided by the square of his or her height [meters]). A BMI between 18.5 and 25 kg/m2 is considered by the World Health Organization (WHO) to be normal weight, a BMI between 25 and 30 kg/m2 as overweight, and a BMI of >30 kg/m2 as obese. Although BMI is easy to calculate, it is a poor estimate of fat mass distribution, as muscular individuals or those with more subcutaneous fat may have a BMI as high as individuals with larger intraabdominal (visceral) fat. The latter type of high BMI is associated with substantially higher risk of metabolic and cardiovascular disease. Alternative parameters to more accurately capture visceral fat include waist circumference (WC) and a waist hip ratio (WHR) of >102 cm and 0.9, respectively, for men and >88 cm and >0.8, respectively, for women. WHR has been shown to be superior to BMI for the correct classification of obesity in CKD.Association of obesity with CKD and other renal complicationsNumerous population based studies have shown an association between measures of obesity and both the development and the progression of CKD (Table 1). Higher BMI is associated with the presence(PintoSietsma et al. 733-41) and development(Foster et al. 39-48;Kramer et al. 587-94;Chang et al. 267-75) of proteinuria in individuals without kidney disease. Furthermore, in numerous large population-based studies, higher BMI appears associated with the presence(Pinto-Sietsma et al. 733-41;Ejerblad et al. 1695-702) and development of low estimated GFR,(Gelber et al. 871-80;Foster et al. 39-48;Kramer et al. 587-94) with more rapid loss of estimated GFR over time,(Lu et al. 704-14) and with the incidence of ESRD.(Munkhaugen et al. 638-46;Iseki et al. 1870-76;Vivante et al. 1644-50;Hsu et al. …