Background'Learning by doing' is a learning model based on performing actions and gaining experience. The 'nursing process' is a systematic, rational method for providing nursing care. During their university education, nursing students need to acquire the ability to promote healthy lifestyles.ObjectiveTo determine the effectiveness of a learning strategy based on learning by doing and grounded in the use of the nursing process, on the lifestyle of nursing students.MethodsThis quasi-experimental intervention (before-after), performed over 2011–2022, involved 2300 nursing students at a university nursing school in Spain. The risk factors for chronic diseases—being a smoker, being overweight, or having high blood pressure—to which each student was exposed were recorded. Those positive for at least one risk factor selected companion students as 'support nursing students' who became responsible for designing an individualised care plan to reduce the risk(s) faced. To ensure the correct use of the nursing process, teachers approved and monitored the implementation of the care plans. Whether risk-reduction objectives were met was determined three months later.ResultsThe students with risk factors largely improved their lifestyles (targets for reducing smoking/body weight were met) with the help of their supporting peers.ConclusionsThe learning by doing method demonstrated its effectiveness, improving the lifestyle of at-risk students via the use of the nursing process.