Body weight and metabolic risk factors in patients with type 2 diabetes on a self-selected high-protein low-carbohydrate diet

Purpose We previously reported beneficial glucoregulatory effects of a fully provided carbohydrate-reduced, high-protein (CRHP) diet in patients with type 2 diabetes mellitus (T2DM) in a crossover 2 × 6-week trial, in which patients maintained their body weight. Here, we investigated physiological changes during an additional 6-month period on a self-selected and self-prepared CRHP diet. Methods Twenty-eight patients with T2DM were instructed to consume a CRHP diet (30% of energy from carbohydrate and 30% from protein) for 24 weeks, after an initial 2 × 6-week trial when all food was prepared and provided to them. Patients received dietary advice every 2 weeks. At weeks 0, 6, 12 and 36, they underwent a 3-h intravenous glucose tolerance test, a 4-h mixed meal test, and a 48-h continuous glucose monitoring. Liver, muscle, pancreas, and visceral fat contents were measured by magnetic resonance imaging. Results During the 24-week self-selected diet period (weeks 12–36), body weight, visceral fat, liver fat, and glycated haemoglobin were maintained at the same levels achieved at the end of the fully provided diet period, and were still lower than at baseline ( P < 0.05). Postprandial insulinaemia and insulin secretion were significantly greater ( P < 0.05). At week 36, fasting insulin and C-peptide levels increased ( P < 0.01) and daily glycaemia decreased further ( P < 0.05) when compared with the end of the fully provided diet period. Conclusion Substituting dietary carbohydrate for protein and fat has metabolic benefits in patients with T2DM. These beneficial effects are maintained or augmented over the next 6 months when patients self-select and self-prepare this diet in a dietitian-supported setting. Trial registration ClinicalTrials.gov NCT02764021.