Effects of Carbohydrate Restriction on Body Weight and Glycemic Control in Individuals with Type 2 Diabetes: A Randomized Controlled Trial of Efficacy in Real-Life Settings.

A fully provided, hypocaloric, carbohydrate-reduced high-protein (CRHP) diet compared to a hypocaloric conventional diabetes (CD) diet for 6 weeks improved glycemic control to a greater extent in face of an intended 6% weight loss in individuals with type 2 diabetes mellitus (T2DM). The present 24-week extension of that study reports on the efficacy of CRHP and CD diets in a real-life setting. Sixty-five individuals with T2DM who completed the initial 6-week fully provided diet period (% energy from carbohydrate, protein, and fat was 30/30/40 in CRHP, and 50/17/33 in CD) continued a free-living, dietician guided 24-week period of which 59 individuals completed. The CRHP compared to CD group reported a 4% lower carbohydrate intake and had higher urea excretion by 22% (both p ≤ 0.05) at week 30, suggesting less difference in carbohydrate and protein intake between groups during the 24-week extension compared to week 6. The loss of body weight during the initial 6 weeks was maintained in both groups during the 24-week extension (-5.5 ± 4.5 and -4.6 ± 4.8 kg) as well as HbA1c (-8.4 ± 6.2 and -8.4 ± 6.9 mmol/mol) with no significant differences between groups. The additional benefits on glucoregulation harnessed by carbohydrate restriction under full diet provision for 6 weeks combined with titrated weight loss could not be maintained in a real-life setting of self-prepared diet aiming on similar diets for 6 months.

Weight-loss induced by carbohydrate restriction does not negatively affect health-related quality of life and cognition in people with type 2 diabetes: A randomised controlled trial.

BACKGROUND & AIMS: We evaluated the effect of weight loss induced by dietary carbohydrate restriction on health-related quality of life (HRQoL) and cognition in type 2 diabetes (T2D). METHODS: In this randomised parallel trial, 72 adults with T2D and overweight/obesity (mean ± SD, HbA1c: 57 ± 8 mmol/mol and BMI: 33 ± 5 kg/m2) were randomly assigned to a carbohydrate-reduced high-protein diet (CRHP: C30E%-P30E%-F40E%) or conventional diabetes diet (CD: C50E%-P17E%-F33E%) for 6 weeks, targeting a 6% weight loss. HRQoL was assessed from the short form 36 (SF-36) questionnaire, including physical and mental component summary (PCS and MCS) scores; global cognition, verbal memory, attention and psychomotor speed, and executive function were assessed from a neuropsychological test battery. RESULTS: Both diet groups achieved a 5.8 kg weight loss and improved PCS (median [25th;75th percentiles], CD: 2.7 [1.1; 4.2] vs. CRHP: 2.1 [0.7; 3.7]), with no difference between diets. The CRHP diet resulted in a clinically relevant improvement of MCS, albeit non-significantly different compared with the change after the CD diet (2.0 [-0.7; 4.8], p = 0.15). Global cognition, attention, and verbal memory were unaffected by the CRHP diet, which selectively worsened the Symbol Digit Modality Test assessing psychomotor speed when compared with the CD diet (-4.1 [-7.2;-1.1], p < 0.01). CONCLUSION: Physical health improved by weight loss independently of macronutrient distribution, while mental health and cognition may be affected by the amount of carbohydrate, protein and fat in the diet. Collectively, our data suggest that weight loss through moderate carbohydrate restriction has no clinically important impact on HRQoL and global cognition in patients with T2D. Registered under ClinicalTrials.gov Identifier no. NCT03814694.

Effects of a highly controlled carbohydrate-reduced high-protein diet on markers of oxidatively generated nucleic acid modifications and inflammation in weight stable participants with type 2 diabetes; a randomized controlled trial.

Carbohydrate-restricted diets are increasingly recognized as options for dietary management of type 2 diabetes mellitus (T2DM). We investigated the effects of a carbohydrate-reduced high-protein (CRHP) and a conventional diabetes (CD) diet on oxidative stress and inflammation in weight stable individuals with T2DM. We hypothesized that the CRHP diet would improve markers of oxidatively generated RNA and DNA modifications as well as inflammatory parameters. Thirty participants with T2DM were randomized to 6 weeks of CRHP or CD dietary treatment (30/50 energy percentage (E%) carbohydrate, 30/17E% protein, 40/33E% fat), followed by a cross-over to the opposite diet for a subsequent 6-week period. All meals were provided during the study and body weight was controlled. Diurnal urine samples were collected after 4 weeks on each diet and oxidatively generated RNA and DNA modifications were measured as 8-oxo-7,8-dihydroguanosine (8-oxoGuo) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), respectively. Fasting concentrations of soluble urokinase plasminogen activator receptor, high-sensitivity C-reactive protein, tumor necrosis factor alpha and interleukin-6 were measured before and after 6 weeks of interventions. Compared with the CD diet, the CRHP diet increased 24-hour urinary excretion of 8-oxoGuo by 9.3% (38.6 ± 12.6 vs. 35.3 ± 11.0 nmol/24 h, p = .03), whereas 8-oxodG did not differ between diets (24.0 ± 9.5 vs. 24.8 ± 11.1 nmol/24 h, p = .17). Changes in plasma inflammatory parameters did not differ between CRHP and CD diets, all p ≥ .2. The clinical implications of increased RNA oxidation following a CRHP diet as well as long-term effects of carbohydrate-restriction on markers of oxidatively generated nucleic acid modifications should be a field of future study.