Effectiveness of methods
Although we have many theories, methods and tools, it appears time and again that behavioural change is not easy. See, for example, Ludden and Hermsen (2020) for an overview of types of interventions that have been used for lifestyle change and a discussion of why they are often not effective (enough). Besides the fact that behavioural change is a complex process, there is a lack of knowledge about when, which method / intervention works best and why, partly due to the wide variety of methods within this category. To investigate this, systematically conducted studies are needed to evaluate the effect of interventions on actual behaviour. It is also important to get a picture of the underlying process (mechanisms of action). We also still have relatively little knowledge of how behavioural change can be sustained in the longer term.