Background: Obesity and weight gain after a cancer diagnosis are associated with poorer outcomes. Weight management could help to reduce the risk of mortality and morbidity. We aimed to understand how a cancer diagnosis impacts weight, health-related behaviours, and views on weight management support among people living with and beyond cancer, and who have experience of living with obesity.

Methods: Semi-structured, one-to-one interviews were conducted over the telephone with 19 people who had previously reported a BMI ≥30, and who had been diagnosed with breast, colorectal or prostate cancer. Participants were recruited from two trials that aimed to improve health behaviours among those with cancer (‘ASCOT’ and ‘APPROACH’). We analysed the interviews using reflexive thematic analysis.

Results: The time since participants’ cancer diagnosis varied from nine to 133 months. There were three overarching themes: 1) Experiences of weight change after cancer and responses to this vary; 2) Misperceptions of weight and cancer risk; 3) Potential benefits of introducing weight management for people living with and beyond cancer. Participants had mixed views on whether cancer had influenced their weight. Most felt their weight had decreased during primary treatment but then returned to their pre-diagnosis weight levels. There were some misperceptions around the risk factors for cancer. Most participants were unaware of the relationship between weight and cancer, and a number were resistant to this message. Despite this, most participants wanted to lose weight for general health reasons, and many felt it would be beneficial for healthcare professionals to discuss weight management once primary cancer treatment has ceased. There were mixed views on whether a weight management programme should be tailored for people living with and beyond cancer. Benefits to tailoring included targeted advice and increased social support, while other participants felt that weight management advice is universal to all.

Conclusion: People with excess weight who are living with and beyond cancer desire more weight management support. Tailored support could be developed, and healthcare professionals may be best placed to introduce this support once primary cancer treatment has ceased.