Effects of a 6-month, low-carbohydrate diet on glycaemic control, body composition, and cardiovascular risk factors in patients with type 2 diabetes: An open-label randomized controlled trial

Abstract

Aim: To investigate the efficacy and safety of a non-calorie-restricted low-carbohydrate diet (LCD) on glycaemic control, body composition, and cardiovascular risk factors in patients with type 2 diabetes (T2D) instructed to maintain their non-insulin antidiabetic medication and physical activity.

Materials and methods: In an open-label randomized controlled trial, patients with T2D were randomized 2:1 to either a LCD with a maximum of 20 E% (percentage of total energy intake) from carbohydrates (n = 49) or a control diet with 50-60 E% from carbohydrates (n = 22) for 6 months. Examinations at enrolment and after 3 and 6 months included blood sample analyses, anthropometrics, blood pressure, accelerometer-based assessment of physical activity, and food diaries. Total fat mass and lean mass were determined by dual-energy x-ray absorptiometry scan. The mean difference in change between groups from baseline are reported.

Results: The LCD group decreased carbohydrate intake to 13.4 E% and increased fat intake to 63.2 E%, which was -30.5 ± 2.2 E% lower for carbohydrates and 30.6 ± 2.2 E% higher for fat, respectively, compared with the control group (all P < .001). The LCD reduced HbA1c after 3 months (-8.9 ± 1.7 mmol/mol; P < .0001), and this was maintained after 6 months (-7.5 ± 1.8 mmol/mol; P < .0001) compared with the control diet. The LCD also reduced weight (-3.9 ± 1.0 kg), body mass index (-1.4 ± 0.4 kg/m² ), and waist circumference (-4.9 ± 1.3 cm) compared with the control diet (all P < .01), accompanied by reductions in total fat mass (-2.2 ± 1.0 kg; P = .027) and lean mass (-1.3 ± 0.6 kg; P = .017). No changes in blood lipids or blood pressure were seen after 6 months. The level of physical activity was maintained, and there were no episodes of severe hypoglycaemia.

Conclusion: A non-calorie-restricted LCD high in fat has significant beneficial effects on glycaemic control and body composition, and does not adversely affect cardiovascular risk factors in patients with T2D. Reducing carbohydrate intake to 10-25 E% appears to be an effective and safe nutritional approach with respect to classical cardiovascular risk factors and hypoglycaemia.

Keywords: low-carbohydrate diet; non-calorie-restricted; physical activity; randomized controlled trial; type 2 diabetes.