Aims

To investigate the efficacy and safety of a non-calorie-restricted low-carbohydrate diet (LCD) on glycemic 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.

Material and methods

In an open-label RCT, patients with T2D were randomized 2:1 to either a LCD with a maximum of 20 E% from carbohydrates (n=49) or a control diet with 50-60 E% from carbohydrates (n=22) for 6 months. Examinations at enrollment 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 DXA-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%, 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<0.001). The LCD reduced HbA1c after 3 months (-8.9±1.7 mmol/mol; p<0.0001), and this was maintained after 6 months (-7.5±1.8 mmol/mol; p<0.0001) compared with the control diet. The LCD also reduced weight (-3.9±1.0 kg), BMI (-1.4±0.4 kg/m2) and waist (-4.9±1.3 cm) compared to control diet (all p<0.01), and were accompanied by reductions in total fat mass (-2.2±1.0 kg, p=0.027) and lean mass (-1.3±0.6 kg; p=0.017). No changes in blood lipids or blood pressure were seen after 6 months. Level of physical activity was maintained, and there were no episodes of severe hypoglycemia.

Conclusion

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

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