Background: Consistent evidence supports the efficacy of very low calorie diets (VLCDs) for weight loss and favourable changes in biochemistry. In Australia, VLCD programs are self-initiated and healthcare professional guidance is not mandated. There is a lack of qualitative research to understand the experiences of Australian users.Aim: To describe the experiences and factors associated with the perceived outcomes of using a VLCD program for ≥4 weeks in Australian adults.Methods: A mixed method study using semi-structured interviews and cross-sectional survey data. Adults were eligible if they were consuming at least one VLCD product daily for ≥4 weeks or had ceased consumption within 4 weeks. Interviews were thematically analysed.Results: Weight loss (19 ± 18 kg) and duration of VLCD product use (5 ± 5 months) of the 31 participants (44 ± 11 years, 97% female, 48% BMI >30 kg/m2) were strongly correlated (r = 0.73, P < .001). Participant experiences were influenced by previous weight loss attempts and VLCD program commencement was due to a convergence of internal motivators. Early health-related outcomes were a reinforcing stimulus for continued use. Although participants developed new health behaviours, they felt dependent on the VLCD program for long term weight management. Individual, program structure and environment-related facilitators and barriers were identified. Health care professionals were minimally engaged as peer and online support was preferred.Conclusion: A model of care to support facilitators and overcome barriers would mean more meaningful engagement of health care professionals to ultimately improve the experience, safety, adherence of VLCD program and product users in Australia.