Background The transtheoretical model of change by Prochaska und DiClemente describes individuals moving through a series of stages—precontemplation, contemplation, preparation, action, and maintenance—in the adoption of behaviour changes. The aim of the study is to describe the process of behaviour changes in patients performing a fasting cure over 10 days. The evaluation is performed by using the transtheoretical model and will highlight factors that influence the fasting cure and that can be used to modify the fasting cure. In addition the study investigates which effects fasting cures exert on the willingness to modify the lifestyle and how the effects can be related to other health-related lifestyle modifications. Hypotheses 1. The fasting cure promotes the willingness to modify the lifestyle; the progression is visible in the series of states in the transtheoretical model. 2. Before starting the fasting cure patients show an individually different willingness to modify their health-related lifestyle, i.e. they find themselves in different stages of the transtheoretical model. 3. After the fasting cure patients find themselves on heterogene stages of the transtheoretical model. The model can involve an improvement, a stagnation, or a worsening of the patient's motivation to achieve a sustained effect in modifying the health-related lifestyle. 4. The follow-up, which takes place 4 weeks after finishing the fasting cure, will demonstrate that patients maintain their behaviour change, i.e. there will be no regression in the sense of the transtheoretical model. Methods All patients who entered the fasting cure in the German Clinic for Integrative Medicine (DEKIMED) were interviewed before and after (10th day) the fasting cure regarding their opinion about the fasting cure and their motivation to participate. Four weeks after leaving the clinic patients again were interviewed using a questionnaire. The analysis of the structured interviews was performed between August and October 2008 using a semiquantitative and qualitative analysis method.