Randomised controlled trials (RCTs) of low carbohydrate diets (defined as a maximum of 130g per day equivalent) for at least 12 weeks versus non-low carbohydrate diets in non-hospitalised adult patients with type 2 diabetes mellitus were eligible for inclusion. Trials had to provide information on daily calorie intake and carbohydrate intake. Cross-over trials and trials that used increased fibre or substitution by whole grains were excluded.
The included trials studied various low carbohydrate diets that ranged from 19g to 95g of carbohydrate per day. The control group included low fat diet, low glycaemic index diet, self-selected usual care diet and healthy eating diet. Intervention durations ranged from three to 48 months. Physically activity changes were generally not specified. Trials were published between 2003 and 2009.
The authors did not state how many reviewers undertook study selection.