The prevalence of obesity is increasing and due to its associated co-morbidities (WHO, 2011) obese people are at greater risk of being hospitalised. While it is evident that student nurses will increasingly be caring for obese patients, there has been a scarcity of studies exploring student nurses' conceptualisation of obesity and participation in obese patients' care. The aims of this study were to explore student nurses' care of obese patients and the meaning they assigned to obesity. I utilised an ethnographic approach that included 305 hours of participant observation of student nurses (n=11), qualified nurses (n=11), nurse managers (n=3) and health care assistants (n=10) in three hospital settings in Wales (orthopaedic, gynaecological-surgical, and respiratory). Data also included semi-structured interviews with student nurses (n=7), documentary analysis and the technique of drawing pictures. The thematic analysis generated three themes: 'student nurses' encounters with obese patients', 'constructing the meaning of obesity: the culture and context of care', and 'the consequences of student nurses' involvement with obese patients' care'. Student nurses found the intensity and frequency of their involvement with obese patients' care challenging, particularly in the areas of interaction, food and nutrition, physical care and moving and handling. Integral to their conceptualisation of obesity were student nurses' cultural norms and values, their limited knowledge regarding obese patients' care, professional socialisation, organisational constraints, and patients' contribution to their care. Student nurses felt disempowered because of the emotional and physical labour they experienced when caring for obese patients. In turn, they participated in the exercise of power over obese patients with both intended and unintended consequences. Equally important was the 'covert liking' (Johnson, 1997) that some students felt towards obese patients who engaged in empowering acts of care to compensate for others' controlling behaviours. The findings provided insights into the student experience of caring for obese patients and raised issues related to the role of culture and context of care in student nurses' conceptualisation of obesity. Drawing on Foucault's (1976) notion of power facilitated understanding of the significance of obesity-related discourses and associated power inequalities in clinical practice. Changes in nurse education and practice are proposed to ensure that nurses are adequately prepared to care for obese patients.