title: The effects of weight change on glomerular filtration rate.
abstract: BACKGROUND
  Little is known about the effect of weight loss/gain on kidney function. Analyses are complicated by uncertainty about optimal body surface indexing strategies for measured glomerular filtration rate (mGFR).
  
  
  METHODS
  Using data from the African-American Study of Kidney Disease and Hypertension (AASK), we determined the association of change in weight with three different estimates of change in kidney function: (i) unindexed mGFR estimated by renal clearance of iodine-125-iothalamate, (ii) mGFR indexed to concurrently measured BSA and (iii) GFR estimated from serum creatinine (eGFR). All models were adjusted for baseline weight, time, randomization group and time-varying diuretic use. We also examined whether these relationships were consistent across a number of subgroups, including tertiles of baseline 24-h urine sodium excretion.
  
  
  RESULTS
  In 1094 participants followed over an average of 3.6 years, a 5-kg weight gain was associated with a 1.10 mL/min/1.73 m(2) (95% CI: 0.87 to 1.33; P < 0.001) increase in unindexed mGFR. There was no association between weight change and mGFR indexed for concurrent BSA (per 5 kg weight gain, 0.21; 95% CI: -0.02 to 0.44; P = 0.1) or between weight change and eGFR (-0.09; 95% CI: -0.32 to 0.14; P = 0.4). The effect of weight change on unindexed mGFR was less pronounced in individuals with higher baseline sodium excretion (P = 0.08 for interaction).
  
  
  CONCLUSIONS
  The association between weight change and kidney function varies depending on the method of assessment. Future clinical trials should examine the effect of intentional weight change on measured GFR or filtration markers robust to changes in muscle mass.
authors.affiliation: Division of Nephrology, Geisinger Health System, Danville, PA, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Chang
authors.affiliation: Department of Population Health Sciences, University of Utah, Salt Lake City, UT, USA.
authors.forename: Tom H
authors.initials: TH
authors.lastname: Greene
authors.affiliation: Center for Clinical Investigation, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Xuelei
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Kendrick
authors.affiliation: Division of Nephrology, Loyola University Medical Center, Maywood, NJ, USA.
authors.forename: Holly
authors.initials: H
authors.lastname: Kramer
authors.affiliation: Division of Nephrology and Hypertension, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Jackson
authors.initials: J
authors.lastname: Wright
authors.affiliation: Division of Nephrology, University of Wisconsin, Madison, WI, USA.
authors.forename: Brad
authors.initials: B
authors.lastname: Astor
authors.affiliation: School of Medicine, Division of Nephrology, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Tariq
authors.initials: T
authors.lastname: Shafi
authors.affiliation: Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Toto
authors.affiliation: Division of Nephrology and Hypertension, Vanderbilt University Medical Center, Nashville, TN, USA.
authors.forename: Julia
authors.initials: J
authors.lastname: Lewis
authors.affiliation: Division of General Internal Medicine, Johns Hopkins University, Baltimore, MD, USA Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Appel
authors.affiliation: School of Medicine, Division of Nephrology, Johns Hopkins University, Baltimore, MD, USA Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Morgan
authors.initials: M
authors.lastname: Grams
mesh_terms: D001835:Body Weight; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D007483:Iothalamic Acid / Q000378:metabolism; D007674:Kidney Diseases / Q000503:physiopathology*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D015430:Weight Gain
chemical_list: D007483:Iothalamic Acid
keywords: body surface area; glomerular filtration rate; indexing; obesity; weight