Moderate carbohydrate restriction for 6 weeks modestly improved glycemic control and decreased circulating and intrahepatic triacylglycerol levels more than weight loss alone compared with a conventional diabetes (CD) diet in people with type 2 diabetes (T2D), according to a study in Diabetologia.
The open-label, parallel, randomized controlled trial allocated patients 1:1 to either a hypo-energetic CD diet or a carbohydrate-reduced high-protein (CRHP) diet for 6 weeks, with the goal of achieving a 6% weight loss. Eligible participants were adults with a body mass index (BMI) >25 kg/m2 who were diagnosed with T2D, with glycated hemoglobin (HbA1c) levels of 48 to 97 mmol/mol (6.5%-11.0%), and who were receiving glucose-lowering therapy limited to metformin or dipeptidyl peptidase-4 (DPP-4) inhibitors. The primary outcome was the change in HbA1c between the diet groups.
A total of 67 participants (all White) completed the study—33 were on the CD diet (mean aged 67.0±8.8 years; 18 female), and 34 were on the CRHP diet (mean aged 66.4±6.9 years; 20 male). Both diets reduced body weight by a mean of 5.8 kg, which was successfully maintained at the end of the studies.
HbA1c was reduced after weight loss in both groups, with significantly greater reductions observed with the CRHP diet vs the CD diet (−1.9 [−3.5, −0.3] mmol/mol; −0.18 [−0.32, −0.03]%; P = .018). Comparable reductions were observed in fasting glucose, insulin, C-peptide levels, and whole body insulin resistance as measured by the Homeostatic Model Assessment for Insulin Resistance (HOMA2_IR) in both the CRHP and CD diet groups.
The CRHP diet reduced fasting triacylglycerol concentration by 18% (6, 29) (P < .01) compared with the CD diet.
The reduction in diurnal mean glucose and glucose coefficient of variability was greater with the CRHP diet compared with the CD diet by −0.8 (−1.2, −0.4) mmol/L (P < .001) and −4.1% (−5.9, −2.2)% (P < .001), respectively.
Hepatic fat content was reduced by 51% after the CD diet and 64% after the CRHP diet, with the difference between groups achieving borderline significance (−26 [−45, 0]%, P = .051). Pancreatic fat content was reduced in both diets but to a smaller extent with the CRHP diet vs the CD diet (33 [7,65]%, P = .010).
The researchers acknowledged several study limitations, including the unblinded design and imbalance of sex distribution and DPP-4 inhibitor use between the 2 diet groups. In addition, physical activity was not objectively measured, and the study duration was limited to 6 weeks–which is half the time required for HbA1c reductions to achieve a new steady state. Further, use of multiple testing without adjustment increases the risk of false-positive results.
“These findings indicate that during matched weight loss, moderate carbohydrate restriction with subsequent increases in protein and fat can modestly improve metabolic health in individuals with obesity and type 2 diabetes, at least in the short term,” the researchers commented. “This may be relevant when designing dietary strategies for the management of type 2 diabetes.”
Disclosure: The study was funded in part by Arla Foods amba. Some of the study authors declared affiliations with biotech, pharmaceutical, device, and other companies. Please see the original reference for a full list of authors’ disclosures.
Thomsen MN, Skytte MJ, Samkani A, et al. Dietary carbohydrate restriction augments weight loss-induced improvements in glycaemic control and liver fat in individuals with type 2 diabetes: a randomised controlled trial. Diabetologia. Published online January 7, 2022. doi:10.1007/s00125-021-05628-8