Although it is well known that the most common chronic diseases are caused by unhealthy behaviours such as smoking and drinking alcohol, a sedentary lifestyle and an unbalanced diet; in spite of primary health care (PHC) services having many opportunities to intervene in those lifestyles; and despite the fact that its professionals are convinced that healthy lifestyle promotion by health services has a potential impact that few other interventions could match; the truth is that healthy lifestyle promotion is far from being an integrated element of clinical practice in PHC . The two main reasons for this are: a) insufficient evidence of the effect of interventions and active components on multiple risk behaviours [2, 3]; and b) the difficulties in changing existing practice to include innovative interventions under real-world conditions [4, 5].
To date, interventions on lifestyle modification in PHC have shown mixed results [2, 3]. There is solid evidence proving the effectiveness of brief advice given in PHC in achieving smoking cessation and reductions in alcohol consumption [6–8]. In the case of physical activity, general advice has little effects, while, medical guidance in the form of a written prescription for physical activity results in small or moderate changes even in the long term [9, 10]. However, concerning diet and the simultaneous approach of several behavioural risk factors, there is still insufficient evidence on the effectiveness of the advice given in PHC [11–13]. Even for those lifestyles for which there is evidence of effectiveness, it is not clear which are the effective components of the interventions, and there is high heterogeneity across the results obtained depending on the context and the way in which the interventions are implemented .
Changing people's lifestyles is not easy, because their behaviour is determined by many personal, institutional and environmental factors, which operate and interact at individual, interpersonal and community levels . Consequently, there is a growing recognition of the need to base lifestyle change interventions on relevant behaviour change theories and to follow a suitable process linking intervention techniques and strategies with this theory. This, as well as producing more effective interventions, should make it possible to identify which factors work, how they work and why . Classical planning models such as Precede-Proceed  or more modern ones such as Intervention Mapping and Causal Modelling [17, 18], as well as consensus techniques and constructs of behaviour change  and guidelines such as those of NICE concerning the development of behaviour change interventions , could facilitate this process of mapping and evaluation of theories and effective techniques.
The improvement of preventive clinical practice involves the transferring and dissemination of effective and efficient interventions to real-world clinical conditions . The failure to date in translating identified effective clinical interventions into routine practice represents the gap between what is avoidable or preventable via these interventions and what is achieved in practice. Several types of quality improvement interventions have been developed with the objective of reducing this gap. In general, what has been recommended is the use of multifaceted interventions that include several strategies such audits and feedback, external facilitators, evidence-based educational meetings with active participation and knowledge management. Specifically, in the area of optimisation of prevention services, efficient registration and reminding systems, a revision of professionals' roles, nursing-based programmes, the creation of multidisciplinary teams, integrated care services and collaboration with community resources, have shown positive results [22–34].
However, the evidence on translation of effective preventive interventions, strategies and programmes is at present insufficient or not conclusive . On the one hand, the effectiveness of the majority of these strategies is low or moderate with a high variation in the degree of change achieved. On the other hand, interventions that have had some success are not easily incorporable to the real-world context of health centres . This is why it has been recommended that interventions for the optimisation of preventive clinical practice should be adapted to the real context of each centre and health system: to their needs, characteristics and identified barriers [37–39]. In line with this, recent models concerning translation of evidence into practice propose the optimisation of clinical practice through research [40–42]. Under this framework, research should be used to optimise practice instead of using the practice context to attempt to demonstrate the relevance of previous studies. Interventions should be designed in the same context in which they are going to be executed, with the active participation of the principle players .
There are many challenges in the design, evaluation and transfer of healthy lifestyle promotion to the clinical context, mainly due to the complexity of the interventions [43–45]. They are composed of a large number of elements and are focussed on a variety of interrelated levels: the patient as an individual, health professionals and the organisation that offers health services to the community, in a context that is characterised by work overload and lack of time. In 2000, the Medical Research Council (MRC) of the United Kingdom defined a theoretical and methodological framework for the design and evaluation of this type of complex interventions in the clinical context . This framework, updated in 2008 , uses simultaneously qualitative and quantitative techniques, and is developed in a series of phases, similar to those of clinical drug research, that could be executed in a sequential or iterative manner: a) preclinical or theoretical phase: establishment of theoretical fundamentals and identification of the active components in the evidence base; b) phase I or modelling phase: definition of intervention components, identification of potential barriers to change and of the mechanisms through which interventions should operate; c) phase II or exploratory trial: evaluation of the feasibility and optimisation of the intervention through the execution of quasi-experimental studies; d) phase III or definitive randomised controlled trial, to enable the controlled experimental evaluation of the intervention; e) phase IV or long term implementation phase under real-world conditions. To date, there have been several projects that have successfully applied the MRC framework for the design and evaluation of complex interventions . The conclusions of these studies agree on the usefulness of the MRC framework as a tool for the researchers in the designing, planning and evaluation of innovative interventions to improve health.
In 2006, in order to tackle the problem of integrating health promotion into PHC, the Primary Care Research Unit of the Basque Health Service set up a multidisciplinary team of 12 health professionals: family doctors, paediatricians and nurses in PHC, specialists in preventive medicine, public health, health education, epidemiologists, psychologists and sociologists. Between 2006 and 2007, this group undertook a first preclinical research phase on usefulness of various theoretical models and intervention strategies for health behaviour change (sedentary lifestyle, diet, smoking, alcohol), and identified factors that make their integration in PHC difficult . In line with the conclusions of this work, the objective of the research protocol reported here is the modelling and planning of interventions which are hypothetically feasible and effective for healthy lifestyle promotion in PHC, following four fundamental principles: (1) cooperation between primary care professionals, community partners and researchers, from the design stage; (2) reorganisation of the PCCs in order to facilitate the incorporation of health promotion; (3) adoption of a socio-ecological model, in which the health service plays an important role, complementary to that of other sectors and non-health resources; and (4) use of an appropriate methodological framework for the design and evaluation of complex interventions .