title: Renal function following three distinct weight loss dietary strategies during 2 years of a randomized controlled trial.
abstract: OBJECTIVE
  This study addressed the long-term effect of various diets, particularly low-carbohydrate high-protein, on renal function on participants with or without type 2 diabetes.
  
  
  METHODS
  In the 2-year Dietary Intervention Randomized Controlled Trial (DIRECT), 318 participants (age, 51 years; 86% men; BMI, 31 kg/m(2); mean estimated glomerular filtration rate [eGFR], 70.5 mL/min/1.73 m(2); mean urine microalbumin-to-creatinine ratio, 12:12) with serum creatinine <176 μmol/L (eGFR ≥ 30 mL/min/1.73 m(2)) were randomized to low-fat, Mediterranean, or low-carbohydrate diets. The 2-year compliance was 85%, and the proportion of protein intake significantly increased to 22% of energy only in the low-carbohydrate diet (P < 0.05 vs. low-fat and Mediterranean). We examined changes in urinary microalbumin and eGFR, estimated by Modification of Diet in Renal Disease and Chronic Kidney Disease Epidemiology Collaboration formulas.
  
  
  RESULTS
  Significant (P < 0.05 within groups) improvements in eGFR were achieved in low-carbohydrate (+5.3% [95% CI 2.1-8.5]), Mediterranean (+5.2% [3.0-7.4]), and low-fat diets (+4.0% [0.9-7.1]) with similar magnitude (P > 0.05) across diet groups. The increased eGFR was at least as prominent in participants with (+6.7%) or without (+4.5%) type 2 diabetes or those with lower baseline renal function of eGFR <60 mL/min/1.73 m(2) (+7.1%) versus eGFR ≥ 60 mL/min/1.73 m(2) (+3.7%). In a multivariable model adjusted for age, sex, diet group, type 2 diabetes, use of ACE inhibitors, 2-year weight loss, and change in protein intake (confounders and univariate predictors), only a decrease in fasting insulin (β = -0.211; P = 0.004) and systolic blood pressure (β = -0.25; P < 0.001) were independently associated with increased eGFR. The urine microalbumin-to-creatinine ratio improved similarly across the diets, particularly among participants with baseline sex-adjusted microalbuminuria, with a mean change of -24.8 (P < 0.05).
  
  
  CONCLUSIONS
  A low-carbohydrate diet is as safe as Mediterranean or low-fat diets in preserving/improving renal function among moderately obese participants with or without type 2 diabetes, with baseline serum creatinine <176 μmol/L. Potential improvement is likely to be mediated by weight loss-induced improvements in insulin sensitivity and blood pressure.
authors.affiliation: Brigham and Women’s Hospital, Harvard School of Public Health, Boston, Massachusetts, USA.
authors.forename: Amir
authors.initials: A
authors.lastname: Tirosh
authors.forename: Rachel
authors.initials: R
authors.lastname: Golan
authors.forename: Ilana
authors.initials: I
authors.lastname: Harman-Boehm
authors.forename: Yaakov
authors.initials: Y
authors.lastname: Henkin
authors.forename: Dan
authors.initials: D
authors.lastname: Schwarzfuchs
authors.forename: Assaf
authors.initials: A
authors.lastname: Rudich
authors.forename: Julia
authors.initials: J
authors.lastname: Kovsan
authors.forename: Georg M
authors.initials: GM
authors.lastname: Fiedler
authors.forename: Matthias
authors.initials: M
authors.lastname: Blüher
authors.forename: Michael
authors.initials: M
authors.lastname: Stumvoll
authors.forename: Joachim
authors.initials: J
authors.lastname: Thiery
authors.forename: Meir J
authors.initials: MJ
authors.lastname: Stampfer
authors.forename: Iris
authors.initials: I
authors.lastname: Shai
mesh_terms: D000328:Adult; D000419:Albuminuria / Q000652:urine; D003404:Creatinine / Q000652:urine; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D050528:Diet, Carbohydrate-Restricted; D018752:Diet, Fat-Restricted; D038441:Diet, Mediterranean; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000502:physiology*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000178:diet therapy*; D010349:Patient Compliance; D051436:Renal Insufficiency, Chronic / Q000178:diet therapy / Q000503:physiopathology; D015431:Weight Loss
chemical_list: D003404:Creatinine