Semi-Crossover Randomised Controlled Trial Design

The semi-crossover design provides an ethical advantage by ensuring control participants eventually receive the intervention and a statistical advantage through within-group comparisons. The total sample size of 28 participants accounts for an expected 30% dropout rate. Randomisation is stratified by IBD diagnosis (CD vs UC) using a randomised block design with block size 4. The trial is a single-centre, open-label, semi-crossover RCT conducted at the Affiliated Lihuili Hospital of Ningbo University, with 28 participants randomised 1:1. Full blinding of participants and researchers is not possible, but outcome assessors and laboratory personnel are kept unaware of group assignments. Trial limitations include small sample size, open-label design, and a 12-week intervention period that may be insufficient to assess sustained behavioural change or disease-modifying effects.