Renal function following three distinct weight loss dietary strategies during 2 years of a randomized controlled trial.
Study Goal
The researchers aimed to determine the long-term effects of a low-carbohydrate high-protein diet on renal function in participants with or without type 2 diabetes.
Results Summary
The study found that a low-carbohydrate diet improved estimated glomerular filtration rate (eGFR) similarly to Mediterranean and low-fat diets, with no significant differences between groups. Improvements were mediated by weight loss-induced enhancements in insulin sensitivity and blood pressure.
Population
Moderately obese participants (mean BMI 31 kg/m²) with or without type 2 diabetes and baseline serum creatinine <176 μmol/L.
Effective Dosage
Protein intake increased to 22% of energy in the low-carbohydrate diet.
Duration
2 years
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
low-carbohydrate diet | increase | proportion of protein intake | participants | 22% of energy | significantly increased | #1 |
low-carbohydrate diet | increase | estimated glomerular filtration rate (eGFR) | participants | +5.3% [95% CI 2.1-8.5] | improvements | #2 |
Mediterranean diet | increase | estimated glomerular filtration rate (eGFR) | participants | +5.2% [3.0-7.4] | improvements | #3 |
low-fat diet | increase | estimated glomerular filtration rate (eGFR) | participants | +4.0% [0.9-7.1] | improvements | #4 |
low-carbohydrate, Mediterranean, and low-fat diets | increase | estimated glomerular filtration rate (eGFR) | participants with type 2 diabetes | +6.7% | improvements | #5 |
low-carbohydrate, Mediterranean, and low-fat diets | increase | estimated glomerular filtration rate (eGFR) | participants without type 2 diabetes | +4.5% | improvements | #6 |
low-carbohydrate, Mediterranean, and low-fat diets | increase | estimated glomerular filtration rate (eGFR) | participants with baseline eGFR <60 mL/min/1.73 m(2) | +7.1% | improvements | #7 |
low-carbohydrate, Mediterranean, and low-fat diets | increase | estimated glomerular filtration rate (eGFR) | participants with baseline eGFR ≥ 60 mL/min/1.73 m(2) | +3.7% | improvements | #8 |
- | decrease | fasting insulin | - | β = -0.211 | decrease | #9 |
- | decrease | systolic blood pressure | - | β = -0.25 | decrease | #10 |
low-carbohydrate, Mediterranean, and low-fat diets | decrease | urine microalbumin-to-creatinine ratio | participants | - | improved | #11 |
low-carbohydrate, Mediterranean, and low-fat diets | decrease | urine microalbumin-to-creatinine ratio | participants with baseline sex-adjusted microalbuminuria | -24.8 | improved | #12 |
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. RESEARCH DESIGN AND 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.