Purpose This study aims to explore the ethical challenges of managing the weight of psychiatric patients in the least restrictive manner in secure mental health settings and whether these could be considered as a source of moral distress for health practitioners, which may be linked to staff burnout and ultimately lead to suboptimal patient care. Design/methodology/approach A qualitative semi-structured interview study design was used to explore the understanding, views and experiences of six staff members working on two medium-secure wards in a UK mental health hospital using an opportunity sampling technique and Interpretative Phenomenological Analysis. Findings Analysis of semi-structured interviews revealed a multitude of moral events that evoked feelings of frustration, powerlessness and anxiety related to the management of obesity in the least restrictive way, which is indicative of moral distress. Research limitations/implications Due to the small sample size and the qualitative nature of the research, the findings of this study are of explorative in nature. Further quantitative research would be required to establish a causative link between the ethical challenges associated with obesity management and staff’s moral distress. Practical implications Addressing the health-care professionals’ knowledge deficit on how to achieve the right balance in their duty of care through inclusion of bioethics into professional discussions and training could improve staff’s well-being and the organisation’s ethical climate. Originality/value To the best of the authors’ knowledge, this is the first qualitative work exploring the role of least restrictive practice in the challenges associated with health promotion within secure psychiatric settings, and the effect these challenges have on mental health staff.