A Very Low-Carbohydrate, Low–Saturated Fat Diet for Type 2 Diabetes Management: A Randomized Trial

OBJECTIVE To comprehensively compare the effects of a very low-carbohydrate, high–unsaturated/low–saturated fat diet (LC) with those of a high–unrefined carbohydrate, low-fat diet (HC) on glycemic control and cardiovascular disease (CVD) risk factors in type 2 diabetes (T2DM). RESEARCH DESIGN AND METHODS Obese adults (n = 115, BMI 34.4 ± 4.2 kg/m2, age 58 ± 7 years) with T2DM were randomized to a hypocaloric LC diet (14% carbohydrate [<50 g/day], 28% protein, and 58% fat [<10% saturated fat]) or an energy-matched HC diet (53% carbohydrate, 17% protein, and 30% fat [<10% saturated fat]) combined with structured exercise for 24 weeks. The outcomes measured were as follows: glycosylated hemoglobin (HbA1c), glycemic variability (GV; assessed by 48-h continuous glucose monitoring), antiglycemic medication changes (antiglycemic medication effects score [MES]), and blood lipids and pressure. RESULTS A total of 93 participants completed 24 weeks. Both groups achieved similar completion rates (LC 79%, HC 82%) and weight loss (LC −12.0 ± 6.3 kg, HC −11.5 ± 5.5 kg); P ≥ 0.50. Blood pressure (−9.8/−7.3 ± 11.6/6.8 mmHg), fasting blood glucose (−1.4 ± 2.3 mmol/L), and LDL cholesterol (−0.3 ± 0.6 mmol/L) decreased, with no diet effect (P ≥ 0.10). LC achieved greater reductions in triglycerides (−0.5 ± 0.5 vs. −0.1 ± 0.5 mmol/L), MES (−0.5 ± 0.5 vs. −0.2 ± 0.5), and GV indices; P ≤ 0.03. LC induced greater HbA1c reductions (−2.6 ± 1.0% [−28.4 ± 10.9 mmol/mol] vs. −1.9 ± 1.2% [−20.8 ± 13.1 mmol/mol]; P = 0.002) and HDL cholesterol (HDL-C) increases (0.2 ± 0.3 vs. 0.05 ± 0.2 mmol/L; P = 0.007) in participants with the respective baseline values HbA1c >7.8% (62 mmol/mol) and HDL-C <1.29 mmol/L. CONCLUSIONS Both diets achieved substantial improvements for several clinical glycemic control and CVD risk markers. These improvements and reductions in GV and antiglycemic medication requirements were greatest with the LC compared with HC. This suggests an LC diet with low saturated fat may be an effective dietary approach for T2DM management if effects are sustained beyond 24 weeks.