A six-month low-carbohydrate diet high in fat does not adversely affect endothelial function or markers of low-grade inflammation in patients with type 2 diabetes: an open-label randomized controlled trial.

BACKGROUND: While a low-carbohydrate diet (LCD) reduces HbA1c in patients with type 2 diabetes (T2D), the associated high intake of fat may adversely affect cardiovascular risk factors. To address this, we examined the effect of a non-calorie-restricted LCD high in fat on endothelial function and markers of low-grade inflammation in T2D over 6 months. METHODS: In an open-label randomized controlled trial, 71 patients with T2D were randomized 2:1 to either a LCD (< 20 E% carbohydrates, 50-60 E% fat) or a control diet (50-60 E% carbohydrates, 20-30 E% fat) for six months. Flow-mediated vasodilation (FMD) and nitroglycerine-induced vasodilation (NID) were assessed by ultrasound in the brachial artery together with plasma interleukin-6 (IL-6) and serum high-sensitivity C-reactive protein (hsCRP) in the participants at baseline (n = 70) and after six months (n = 64). RESULTS: The FMD and NID were unaltered in both groups after six months, and there were no between-group differences in change of either FMD (p = 0.34) or NID (p = 0.53) in response to the interventions. The circulating hsCRP and IL-6 levels decreased only in response to LCD (both p < 0.05). However, comparing changes over time with the control diet, the LCD did not reduce either IL-6 (p = 0.25) or hsCRP (p = 0.07) levels. The lack of changes in FMD and NID in response to LCD persisted after adjustment for cardiovascular risk factors. CONCLUSION: A LCD high in fat for six months does not adversely affect endothelial function or selected markers of low-grade inflammation, which suggests that this nutritional approach does not increase the risk of cardiovascular disease. Trial registration ClinicalTrials.gov (NCT03068078).

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.

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.