Randomised crossover controlled trial of dietary interventions for glycaemic control when body weight is kept stable.

A Palaeolithic diet is an efficacious dietary approach for glycaemic control in type 2 diabetes. Causal mechanisms are body weight loss and glucometabolic effects from differences in included food groups, macronutrient composition, fibre content, and glycaemic load. The aim was to test the hypothesis that characteristic food group differences between a Palaeolithic and a diabetes diet would cause an effect on glycaemic control when weight was kept stable and diets were matched for macronutrient composition, fibre content and glycaemic load. Adult participants with type 2 diabetes and increased waist circumference were instructed to follow two diets, with or without the food groups cereal grain, dairy products, and legumes, during two periods of 4 weeks separated by a 6-week washout period in a random-order crossover design. The Palaeolithic diet included fruit, vegetables, tubers, fish, shellfish, lean meat, nuts, eggs and olive oil, and excluded cereal grains, dairy products and legumes. The diabetes diet included fruit, vegetables, fish, shellfish, lean meat, nuts, eggs, olive oil, and substantial amounts of whole grains, low-fat dairy products and legumes. Dietary energy content was adjusted throughout the study to maintain stable body weight. There were no differences between diets on HbA1c or fructosamine among the 14 participants. Body weight was kept stable, and the two diets were successfully matched for macronutrient composition and glycaemic load but not for fibre content. Characteristic food group differences and the accompanying differences in fibre content between a Palaeolithic and a diabetes diet do not cause an effect on glycaemic control.