Optimised carbohydrate dietary intervention for improving metabolic health in adults with prediabetes: study protocol for a multicentre randomised controlled trial.

Abstract

Dietary modification is an important strategy for the prevention of type 2 diabetes, with fibre intake recognised as a key factor in promoting metabolic health. Resistant starch (RS), a type of fermentable dietary fibre, has emerged as a promising therapeutic approach due to its association with weight loss, enhanced insulin sensitivity and improved glucose metabolism. As nutritional research progresses, the focus has shifted from individual nutrients to overall dietary patterns. Based on this concept, this study aims to investigate the metabolic effects of a dietary pattern that optimises carbohydrate structure by increasing RS intake and reducing rapidly digestible carbohydrate in adults with pre-diabetes. This is a multicentre, randomised, parallel-controlled clinical trial, which will enrol 250 adults diagnosed with pre-diabetes. Eligible participants will undergo randomisation to receive either a guideline-based conventional diet or an optimised carbohydrate diet (OCD). In the OCD intervention, daily RS intake will be increased to approximately 40 g, with fibre intake rising to 20-40 g per 1000 kcal. At the same time, the intake of rapidly digestible starch and free sugars will be reduced. The intervention will last for 6 months, followed by a 3-month post-intervention follow-up period. The primary outcome is the change in postprandial glycaemic response, assessed using the incremental area under the curve (iAUC) for plasma glucose during the oral glucose tolerance test (OGTT). Secondary outcomes include the proportion of participants achieving remission to normoglycaemia or progressing to type 2 diabetes, changes in other glucose- and lipid-related metabolic parameters and changes in lifestyle-related behavioural factors. Exploratory outcomes will include changes in appetite-related hormones, circulating cytokines, immune function and multi-omics profiles. This study was approved by 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) and registered in the Chinese Clinical Trial Registry. Findings from this study will be disseminated in peer-reviewed journal publications. ChiCTR2500113583.