Experiences of a food-based very low-calorie diet programme among Chinese adults with obesity and prediabetes or type 2 diabetes: a COM-B-guided qualitative study

Very low-calorie diets (VLCDs) can halt the progression of type 2 diabetes mellitus (T2DM) and induce remission. However, they currently face significant adherence challenges, limited long-term efficacy, and acceptability issues among Chinese populations due to cultural differences. Aiming to explore the perceptions, experiences of individuals with obesity and prediabetes or T2DM who are consuming VLCDs, this descriptive qualitative study was conducted guided by the Capability, Opportunity, Motivation-Behaviour (COM-B) model. Purposeful sampling selected participants at two hospitals in China between July and August 2024. Data were collected through semi-structured interviews and analyzed via a COM-B–guided framework analysis. Fourteen participants completed the interviews, revealing 8 subthemes: (1) Capability factors: A lack of self-control hinders adherence to dietary routines, whereas limited physical ability restricts engagement in daily exercise; (2) Opportunity factors: Supportive physical environments and strong social networks facilitate the maintenance of health behaviours, whereas competing life priorities often lead to the neglect of health management; (3) Motivation factors: The perceived threat of disease and positive treatment feedback enhance behavioural motivation, whereas discomfort and negative experiences related to dietary restriction undermine adherence sustainability. Future research should focus on developing targeted and sustainable lifestyle management programmes to enhance dietary compliance and diabetes management outcomes.