Dietary modification is a foundational approach for preventing progression from pre-diabetes to type 2 diabetes. Growing evidence highlights the role of dietary fibre in supporting metabolic health, and among fibres, resistant starch (RS)—a fermentable form of dietary fibre—has attracted attention for potential benefits including weight reduction, enhanced insulin sensitivity and improved glucose metabolism. Nutritional research is increasingly emphasising whole dietary patterns rather than single nutrients. This trial applies that perspective by testing a dietary pattern that deliberately alters carbohydrate structure: increasing RS intake while reducing rapidly digestible carbohydrates and free sugars.
This study is a multicentre, randomised, parallel-controlled clinical trial planned to enrol 250 adults diagnosed with pre-diabetes. Eligible participants will be randomised to one of two arms: a guideline-based conventional diet or an optimised carbohydrate diet (OCD). The design aims to compare the metabolic effects of a diet that modifies carbohydrate quality and fermentable fibre content against usual guideline-based dietary advice in people at high risk of developing type 2 diabetes.
Participants allocated to the control arm will receive a guideline-based conventional diet consistent with usual dietary recommendations reported in the study. The intervention arm will receive an optimised carbohydrate diet (OCD) in which carbohydrate quality is restructured to increase fermentable fibre intake and reduce rapidly digested carbohydrate sources. Specific dietary advice, monitoring and support consistent with the trial protocol will be provided to achieve the targeted dietary changes.
The OCD intervention is specified to raise daily resistant starch intake to approximately 40 g per day. Overall fibre targets in the OCD are set to 20–40 g per 1000 kcal. Concurrently, the diet reduces intake of rapidly digestible starches and free sugars. The source text does not provide additional detail on food items, meal plans or strategies for achieving these nutrient targets; those protocol specifics were not reported in the source.
The dietary intervention will be delivered over a 6-month period. After completing the intervention phase, participants will enter a 3-month post-intervention follow-up to assess the persistence of effects and any delayed changes in metabolic or behavioural outcomes.
The principal outcome measure is the change in postprandial glycaemic response. This will be quantified as the incremental area under the curve (iAUC) for plasma glucose obtained during an oral glucose tolerance test (OGTT). The iAUC during OGTT is the trial’s predefined primary endpoint for assessing changes in glucose handling after the dietary intervention.
Secondary outcomes include the proportion of participants who remit to normoglycaemia or who progress to overt type 2 diabetes over the study period. Additional secondary endpoints cover changes in other glucose- and lipid-related metabolic parameters and modifications in lifestyle-related behavioural factors. The source did not provide a full itemised list of all secondary biomarkers or specific measurement schedules beyond these domains.
Exploratory analyses will investigate broader biological signals that may mediate or reflect dietary effects. Planned exploratory outcomes include changes in appetite-related hormones, circulating cytokines, measures of immune function and multi-omics profiles. The protocol text provided does not report specific assays, platforms or analytic plans for the multi-omics investigations.
Ethics approval for the trial was obtained from the Ethics Committee of Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine (Approval No. 2025-122; Protocol V.1.0, 20250811) and the Ethics Committee of Shenzhen Center for Chronic Disease Control (Approval No. SZCCC-2024-011-01-PJ). The trial is registered in the Chinese Clinical Trial Registry under number ChiCTR2500113583. The investigators plan to disseminate findings through peer-reviewed journal publications. The source did not report timelines for publication or dissemination venues.