Low-energy diets differing in fibre, red meat and coffee intake equally improve insulin sensitivity in type 2 diabetes: a randomised feasibility trial

Abstract

Aims/hypothesis Epidemiological studies have found that a diet high in fibre and coffee, but low in red meat, reduces the risk for type 2 diabetes. We tested the hypothesis that these nutritional modifications differentially improve whole-body insulin sensitivity (primary outcome) and secretion. acarbose and known disease duration of ≤5 years. Exclusion criteria were: HbA 1c >75 mmol/mol (9.0%), type 1 or secondary diabetes types and acute or chronic diseases including cancer. Patients taking any medication affecting the immune system or insulin sensitivity, other than metformin, were also excluded. Of 59 patients (randomised using randomisation blocks [four or six patients] with consecutive numbers), 37 (54% female) obese type 2 diabetic patients completed this controlled parallel-group 8-week low-energy dietary intervention. The participants consumed either a diet high in cereal fibre (whole grain wheat/rye: 30-50 g/day) and coffee (≥5 cups/day), and free of red meat (L-RISK, n=17) or a diet low in fibre (≤10 g/day), coffee-free and high in red meat (≥150 g/ day) diet (H-RISK, n=20). Insulin sensitivity and secretion were assessed by hyperinsulinaemic-euglycaemic clamp and intravenous glucose tolerance tests with isotope dilution. Whole-body and organ fat contents were measured by magnetic resonance imaging and spectroscopy. Conclusions/interpretation No evidence of a difference between both low-energy diets was identified. Thus, energy restriction per se seems to be key for improving insulin action in phases of active weight loss in obese type 2 diabetic patients, with a potential improvement of subclinical inflammation with the L-RISK diet. Trial Registration: Clinicaltrials.gov NCT01409330

Effect of Low-Energy Diets Differing in Fiber, Red Meat, and Coffee Intake on Cardiac Autonomic Function in Obese Individuals With Type 2 Diabetes

“…Multiple linear regression analyses with adjustments for sex, age, and BMI were performed to determine associations between two variables. The primary outcome for this pilot study was the change in whole-body insulin sensitivity to obtain effect size and variance estimates for both diets (20). The primary outcome measures were pNN50 (representing the time-domain HRV measures) and low-frequency/high-frequency ratio (representing the frequency-domain HRV measures).…”

“…The details of the study protocol have been reported elsewhere (20). In brief, volunteers invited to the German Diabetes Center were 1:1 randomly allocated to one of two dietary interventions using randomization blocks (four or six patients) with consecutive numbers.…”

“…Moreover, participants received a financial compensation for their time spent in the study center during baseline/follow-up visits. The weekly visits also included monitoring of body weight, hip and waist circumference, blood pressure, and blood sampling, as previously reported (20). Since this trial was designed as a pilot study, a statistical power calculation was not performed (20).…”

“…The weekly visits also included monitoring of body weight, hip and waist circumference, blood pressure, and blood sampling, as previously reported (20). Since this trial was designed as a pilot study, a statistical power calculation was not performed (20). Post hoc statistical power calculation revealed that 132 (80% power), 176 (90% power), and 217 (95% power) subjects would be needed in each group to detect a significant difference for the change in the low-frequency/highfrequency ratio from baseline to 8 weeks between the groups.…”

“…Plasma coffeederived compounds (caffeine and its metabolites, theophylline, theobromine, and paraxanthine, and the polyphenols caffeic acid and its metabolites, dihydrocaffeic acid, ferulic acid, dihydroferulic acid, isoferulic acid, dihydroisoferulic acid, dihydro-3-coumaric acid, 3-(3,4-dimethoxyphenyl)propionic acid, 3,4-dimethylcaffeic acid, and 3-coumaric acid) were determined using highperformance liquid chromatography and GC-MS (25). The two main urinary alkylresorcinol metabolites, 3,5-dihydroxybenzoic acid and 3-(3,5-dihydroxyphenyl)-propanoic acid, were analyzed using GC-MS, as previously reported (20).…”