BMC Public Health 2009, 9:207 http://www.biomedcentral.com/1471-2458/9/207 The quantitative element will be complemented by a longitudinal qualitative study elucidating pathways of influence between intervention activities and health outcomes. A related element of the study investigates the health-related aspects of the structural and ecological characteristics of the project areas. The project 'process' will also be evaluated. Discussion: The size of the project and the fact that the interventions are 'complex' in the sense that firstly, there are a number of interacting components with a wide range of groups and organisational levels targeted by the intervention, and secondly, a degree of flexibility or tailoring of the intervention, makes this trial potentially very useful in providing evidence of the types of activities that can be used to address chronic health problems in communities suffering from multiple deprivation. Trial Registration: Current Controlled Trials ISRCTN68175121 Background The incidence of many chronic diseases such as cancer, cardiovascular diseases, and diabetes is strongly influ- enced by unhealthy lifestyles including poor diets and sedentariness [1-3]. In the UK, 10% and 3% of all DALYs are attributed to poor diet and insufficient physical activ- ity respectively [4,5]. These translate into direct costs to the NHS of £6 billion for diet and £1.06 billion for phys- ical inactivity related ill-health. These estimates do not include the indirect costs of illness-related lost productiv- ity. The 2004 Wanless Report 'Securing good health for the whole population'[6] and the 2004 White Paper: 'Choos- ing Health' [7] emphasised the importance of encourag- ing individuals to follow healthy lifestyles as a key way to improve health, address health inequalities and to pre- vent escalation of NHS costs. Healthy eating (HE) and healthy physical activity (HPA) were emphasised as key components of a healthy lifestyle. There is also increasing recognition that many structural, cultural and environmental factors outside the individ- ual's control constrain their ability to adopt a healthier lifestyle [8]. This is reflected in the development of eco- logic models [9] where environmental influences or con- straints on behaviour are seen as important determinants of health and health inequalities. Pertinent examples include lack of access to healthy food sources at affordable prices and unsafe environments in which to take physical exercise. Certain ethnic groups also face cultural con- straints to their adoption of healthier lifestyles. The recent Sport England survey 'Active People' showed that those who identified themselves as South Asian or African-Car- ibbean were less likely to meet the recommended levels of physical activity than White European groups [10]. Black Minority Ethnic (BME) communities are often those with the poorest health status. Low income and poor physical environments also impact on mental health (MH) [11]. Poor mental health is corre- lated with poor physical health, social exclusion, work- lessness and poverty along with other indicators of social or economic stress such as recent migration. Interventions promoting mental health have focused on strengthening the protective factors – a supportive family and a job with some degree of control – and reducing the effect of health risks – such as a family history of psychiatric disorders or financial stress [12]. There is also a literature on the com- munity-level and environmental influences on mental health indicating the potential for interventions promot- ing wellbeing at these levels[13]. Public spending on men- tal health services was estimated at £7.9 billion in 2002/3 though again indirect costs will be much higher [14]. However, the evidence for public health interventions aimed at HPA, HE and MH is weak. This is particularly the case for 'complex' interventions, where the 'active compo- nent' of the intervention is not clear[15]. Gaps in evidence also exist for programmes aimed at dis- advantaged or BME groups, activities to change structural or ecological factors and interventions designed to work through 'community development' approaches. These are the types of interventions implemented under the Well London project presented in this paper. The Well London project The Well London project is a four-year programme that uses a community development approach to deliver a set of complex health interventions aimed at improving HE, HPA and MH in the most deprived neighbourhoods of 20 London Boroughs. The project is led by The Greater Lon- don Authority with the London Health Commission and a consortium of partners including Groundwork London, the London Sustainability Exchange (LSx), the Central YMCA, the University of East London, the South London and Maudsley NHS Foundation Trust (SLaM) and the Arts Council for England. These partners together form the Well London Alliance. The project was launched at the end of 2007 and the interventions, developed in detailed consultation with communities, local authorities (LAs), Page 2 of 11 (page number not for citation purposes)