Background: Obesity has been identified as a major health concern in adults with intellectual disabilities. This study evaluates a health promotion programme delivered by a NHS department for adults with intellectual disabilities. Method: Routine NHS data were collated and analysed descriptively. One hundred and ninety one adults with intellectual disabilities were screened and monitored over a 2-year period, with a sequence of health and fitness tests. Attendance rates and body mass index (BMI) were the principal outcome measures for this evaluation. Results: 69% of the samples were overweight/obese/morbidly obese at the beginning of the programme. Despite attendance at intermediate follow-up clinics, 21% of the sample failed to attend at year 1 and 34% failed to attend at year 2 clinics. In terms of BMI changes at year one, 52% of the "at risk" BMI category remained static, 26.7% showed a worsening weight status and 20.7% showed an improving weight status. At year 2, 52.1% of the "at risk" BMI category remained static, while 22% got worse and 25% showed an improvement in weight status. Conclusions: This study illustrates the possibilities and difficulties of devising an effective health promotion model within the NHS framework. For long-term obesity-specific interventions to be successful, further research is needed into multi-disciplinary programmes which incorporate the primary carers and are responsive to NICE guidelines.