Introduction Much of the science behind dietary guidelines for risk reduction and chronic disease management is equivocal, and there are well-accepted uncertainties and complexities relating to diet in everyday life, as well as physiological processes. Guidelines have therefore stopped short of aligning with one particular approach, instead highlighting several evidence-based options. However, reduced carbohydrate, or ‘low-carb’, diets have increasing traction in the media and with patients, practitioners and the general public. This qualitative study examines healthcare practitioner (HCP) experiences of implementing a reduced carbohydrate diet.

Methods Semistructured, qualitative interviews were conducted with 19 HCPs in the UK family practice (including general practitioners, practice nurses and non-medical practitioners), recruited through a special interest forum, and social media. Data analysis employed social science theory and methods to produce key themes.

Results All participants self-identified as ‘low-carb practitioners’ who, over time, had introduced a specific focus around carbohydrate reduction into their work. They reported transformations in patients’ metabolic markers, patient enthusiasm for the approach and renewed job satisfaction. Key themes highlight experiences of: (1) discovering low-carb as a new ‘tool-in-the-box’; (2) promoting and supporting incremental low-carb experimentation; and (3) diverging from established dietary guidelines.

Conclusions This study provides important experience-based evidence on a topical dietary intervention. Participants strongly advocated for the use of low-carb diets. The successes described draw attention to the need for pragmatic, formative evaluation of low-carb advice and support as a ‘complex intervention’ (alongside physiological research), to justify, challenge and/or shape low-carb intervention in clinical practice. The findings raise important questions about the contribution of particular care practices to the apparent success of low-carb. Social science analyses can elucidate how dietary intervention is carried out across different healthcare settings (eg, dietetics, endocrinology) and patient groups, how healthcare practices intersect with people’s everyday self-management and how different forms of evidence are invoked and prioritised.