Description: Background Specialist Lifestyle Management (SLiM) is a structured patient education and self-management group weight management programme. Each session is run monthly over a 6-month period providing a less intensive long-term approach. The groups are patient-centred incorporating educational, motivational, behavioural and cognitive elements. The theoretical background, programme structure and preliminary results of SLiM are presented. Subjects/methods The study was a pragmatic service evaluation of obese patients with a body mass index (BMI) ≥35 kg/m 2 with comorbidity or ≥40 kg/m 2 without comorbidity referred to a specialist weight management service in the West Midlands, UK. 828 patients were enrolled within SLiM over a 48-month period. Trained facilitators delivered the programme. Preliminary anonymised data were analysed using the intention-to-treat principle. The primary outcome measure was weight loss at 3 and 6 months with comparisons between completers and non-completers performed. The last observation carried forward was used for missing data. Results Of the 828 enrolled within SLiM, 464 completed the programme (56%). The mean baseline weight was 135 kg (BMI=49.1 kg/m 2 ) with 87.2% of patients having a BMI≥40 kg/m 2 and 12.4% with BMI≥60 kg/m 2 . The mean weight change of all patients enrolled was –4.1 kg (95% CI –3.6 to –4.6 kg, p=0.0001) at the end of SLiM, with completers (n=464) achieving –5.5 kg (95% CI –4.2 to –6.2 kg, p=0.0001) and non-completers achieving –2.3 kg (p=0.0001). The majority (78.6%) who attended the 6-month programme achieved weight loss with 32.3% achieving a ≥5% weight loss. Conclusions The SLiM programme is an effective group intervention for the management of severe and complex obesity.