Comparison of low- and high-carbohydrate diets for type 2 diabetes management: a randomized trial1234

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ABSTRACT

Background:Few well-controlled studies have comprehensively examined the effects of very-low-carbohydrate diets on type 2 diabetes (T2D).

Objective:We compared the effects of a very-low-carbohydrate, high–unsaturated fat, low–saturated fat (LC) diet with a high-carbohydrate, low-fat (HC) diet on glycemic control and cardiovascular disease risk factors in T2D after 52 wk.

Design:In this randomized controlled trial that was conducted in an outpatient research clinic, 115 obese adults with T2D [mean ± SD age: 58 ± 7 y; body mass index (in kg/m2): 34.6 ± 4.3; glycated hemoglobin (HbA1c): 7.3 ± 1.1%; duration of diabetes: 8 ± 6 y] were randomly assigned to consume either a hypocaloric LC diet [14% of energy as carbohydrate (carbohydrate <50 g/d), 28% of energy as protein, and 58% of energy as fat (<10% saturated fat)] or an energy-matched HC diet [53% of energy as carbohydrate, 17% of energy as protein, and 30% of energy as fat (<10% saturated fat)] combined with supervised aerobic and resistance exercise (60 min; 3 d/wk). Outcomes were glycemic control assessed with use of measurements of HbA1c, fasting blood glucose, glycemic variability assessed with use of 48-h continuous glucose monitoring, diabetes medication, weight, blood pressure, and lipids assessed at baseline, 24, and 52 wk.

Results:Both groups achieved similar completion rates (LC diet: 71%; HC diet: 65%) and mean (95% CI) reductions in weight [LC diet: −9.8 kg (−11.7, −7.9 kg); HC diet: −10.1 kg (−12.0, −8.2 kg)], blood pressure [LC diet: −7.1 (−10.6, −3.7)/−6.2 (−8.2, −4.1) mm Hg; HC diet: −5.8 (−9.4, −2.2)/−6.4 (−8.4, −4.3) mm Hg], HbA1c [LC diet: −1.0% (−1.2%, −0.7%); HC diet: −1.0% (−1.3%, −0.8%)], fasting glucose [LC diet: −0.7 mmol/L (−1.3, −0.1 mmol/L); HC diet: −1.5 mmol/L (−2.1, −0.8 mmol/L)], and LDL cholesterol [LC diet: −0.1 mmol/L (−0.3, 0.1 mmol/L); HC diet: −0.2 mmol/L (−0.4, 0.03 mmol/L)] (P-diet effect ≥ 0.10). Compared with the HC-diet group, the LC-diet group achieved greater mean (95% CI) reductions in the diabetes medication score [LC diet: −0.5 arbitrary units (−0.7, −0.4 arbitrary units); HC diet: −0.2 arbitrary units (−0.4, −0.06 arbitrary units); P= 0.02], glycemic variability assessed by measuring the continuous overall net glycemic action-1 [LC diet: −0.5 mmol/L (−0.6, −0.3 mmol/L); HC diet: −0.05 mmol/L (−0.2, −0.1 mmol/L); P= 0.003], and triglycerides [LC diet: −0.4 mmol/L (−0.5, −0.2 mmol/L); HC diet: −0.01 mmol/L (−0.2, 0.2 mmol/L); P= 0.001] and greater mean (95% CI) increases in HDL cholesterol [LC diet: 0.1 mmol/L (0.1, 0.2 mmol/L); HC diet: 0.06 mmol/L (−0.01, 0.1 mmol/L); P= 0.002].

Conclusions:Both diets achieved substantial weight loss and reduced HbA1c and fasting glucose. The LC diet, which was high in unsaturated fat and low in saturated fat, achieved greater improvements in the lipid profile, blood glucose stability, and reductions in diabetes medication requirements, suggesting an effective strategy for the optimization of T2D management. This trial was registered at www.anzctr.org.auas ACTRN12612000369820.

Keywords:

diabetes
diet
macronutrient composition
obesity
weight loss

ABBREVIATIONS

CONGA-1
continuous overall net glycemic action of observations 1 h apart
CONGA-4
continuous overall net glycemic action of observations 4 h apart
CRP
C-reactive protein
CVD
cardiovascular disease
FFM
fat-free mass
GV
glycemic variability
HbA1c
glycated hemoglobin
HC
high carbohydrate, low fat
HOMA2-IR
homeostasis model assessment of insulin resistance index 2 to assess insulin resistance
HOMA2-%B
homeostasis model assessment index 2 to assess β cell function
LC
very low carbohydrate, high unsaturated fat, low saturated fat
MAGE
mean amplitude of glycemic excursion
MES
medication effect score
SDGlucose
SD of blood glucose
T2D
type 2 diabetes

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1

Some outcome data were presented at Obesity Week 2014: the combined annual meeting of The Obesity Society (TOS) and the American Society for Metabolic & Bariatric Surgery (ASMBS), Boston, MA, 2–7 November 2014; the International Diabetes Federation–Western Pacific Region (IDF-WPR) Congress 2014, Singapore, 21–24 November 2014; Nutrition Society of Australia (NSA) Annual Scientific Meeting, Hobart, Australia, 26–28 November 2014.

2

Supported by the National Health and Medical Research Council of Australia (project grant 103415) and the Agency for Science, Technology and Research, Singapore (postgraduate research scholarship to JT).

3

Funding sponsors had no role in the design, conduct, or reporting of the study or the decision to submit the manuscript for publication.

3

Supplemental Tables 1and 2are available from the “Supplemental data” link in the online posting of the article and from the same link in the online table of contents at http://ajcn.nutrition.org.