Background: The rising issue of obesity is associated with increased risk of morbidity and mortality. The prevention and management of obesity has been problematic, due to its complex and multifaceted aetiology (Foresight, 2007). Lifestyle modification is essential for effective and sustainable weight loss, however high attrition rates are common (Foresight, 2007). The aim of this study was to systematically review the evidence for the effectiveness of lifestyle (diet and exercise) programmes, identifying the features of successful lifestyle weight management programmes, and to explore the experiences of individuals who have attended the Hammersmith Hospitals Lifestyle weight management programme, identifying aspects which promote and prevent successful completion of the programme. Methods: This study consisted of a systematic review and phenomenological observational study of the Hammersmith hospitals NHS trust Lifestyle weight management clinic. The systematic review involved searching four relevant scientific electronic databases: Medline, Embase, Psychinfo, Cochrane Library; 4314 titles, 346 abstracts and 113 full texts were screened. Eight studies met the predetermined search criteria (Dietitian delivered one to one lifestyle interventions with overweight or obese adults reporting weight change). This systematic review focused on clinically significant (≥5%) weight loss (NHS, 2006) as the measure of efficacy and success of lifestyle weight management programmes. The phenomenological observation involved the Lifestyle clinic; a 6 months individualised care package consisted of diet and exercise advice with behaviour change techniques and motivational interviewing, delivered by a dietitian, to promote overweight/obese adults to reduce weight. Purposeful sampling of patients, who had attended the clinic in the last 12 months, was conducted by contacting and requesting for volunteers. In-depth one-to-one interviews with six participants (four completers, two non-completers) were completed and analysed (Colaizzi, 1978) with the assistance of the computer software nVivo 8, which organised coded statements and themes identified. Ethical approval was given by St Mary's Research Ethics Committee, London. Results: Three of the eight studies reviewed demonstrated ≥5% clinically significant weight loss. Key features of all three successful programmes, and not of the five unsuccessful programmes, included frequent weekly follow ups, compulsory supervised exercise and intense dietary counselling and exercise regimens. The phenomenological observation identified a variety of factors; key promoting factors included regular appointments, realistic targets, recognising responsibility, positive attitude and support from others and dietitian. A key inhibiting factor was difficulty with exercise. Discussion: Limitations of the study were: the limited number of studies, the heterogeneous nature of the studies, and the restricted applicability of the studies of the review. Recruitment bias restricting ratio of completers to non-completers, limited sample size, and lack of participant validation of the results/conclusions limited the phenomenological observation. Furthermore it was questionable whether the interventions were sustainable; participants believed lack of support after the 6 months and difficulty exercising inhibited success. Recommendations for practice included continuous regular support, supplementary exercise programmes and optional group support; however practical implications involved are cost, time and resources. Conclusion: Further quantitative and qualitative research with greater samples would be essential to validate this study, ensure data saturation and evaluate weight management interventions.