This study was designed to investigate the impact of initial Body Mass Index (BMI) and motivation for recovery on a 12-week day therapy programme for Eating Disorders. Outcome was assessed by changes in eating disorder symptomology, mood and self-esteem. A battery of assessment questionnaires was given to 34 eating disorder clients on admission to and completion of the programme. This study found that BMI at admission did not affect treatment outcome directly. Only patient self-rated motivation directly affected treatment outcome with more highly motivated clients making more significant changes to their eating disorder symptomology across the programme. However, motivation, BMI and duration of illness influenced how likely a patient was to complete the 12 weeks and completion of the programme had a direct effect on eating disorder symptomology, mood and self-esteem. BMI and motivation can therefore be seen to indirectly effect the outcome of treatment via the ability to complete the programme.