- BACKGROUND: There is a limited evidence on the effectiveness of lifestyle interventions in achieving and maintaining a significant level of weight loss in morbidly obese patients. This study evaluated the impact on weight loss and psychological well-being of a community-based weight management service for morbidly obese patients [body mass index (BMI) ≥35 with related co-morbidities or BMI >40] in Derbyshire county. METHODS: Five hundred and fifty-one participants entered the service since 2010, and 238 participants were still active within the service or had completed the 2-year intervention in April 2013. A one-group pre-post design was used todetermine average weight loss (kg) and impact on mental health and well-being [using the validated clinical outcomes of routine evaluation-outcome measure (CORE-OM) questionnaire] among participants. Measurements were recorded at baseline, 12 weeks, 24 weeks, 1 year, 18 months and 2 years, and significance (P ≤ 0.05) was determined using the paired sample t-test. RESULTS: Statistically significant weight loss was recorded at each measurement point for those participants who remained engaged with the service (4.9 kg weight loss at 12 weeks to 18.2 kg at 2 years). There was a significant positive impact on psychological well-being demonstrated by CORE-OM score. CONCLUSIONS: Findings show clinically and statistically significant weight loss among participants with improvements in physical and mental health.