Clinical trials have shown that providing advice and support for people with excess weight can lead to meaningful weight loss. Despite this evidence and guidelines endorsing this approach, provision in real-world clinical settings remains low. We used Strong Structuration Theory (SST) to understand why people are often not offered weight management advice in primary care in England. Data from policy, clinical practice and focus groups were analysed using SST to consider how the interplay between weight stigma and structures of professional responsibilities influenced clinicians to raise (or not) the issue of excess weight with patients. We found that general practitioners (GPs) often accounted for their actions by referring to obesity as a health problem, consistent with policy documents and clinical guidelines. However, they were also aware of weight stigma as a social process that can be internalised by their patients. GPs identified addressing obesity as a priority in their work, but described wanting to care for their patients by avoiding unnecessary suffering, which they were concerned could be caused by talking about weight. We observed tensions between knowledge of clinical guidelines and understanding of the lived experience of their patients. We interpreted that the practice of 'caring by not offering care' produced the outcome of an absence of weight management advice in consultations. There is a risk that this outcome reinforces the external structure of weight stigma as a delicate topic to be avoided, while at the same time denying patients the offer of support to manage their weight.