With an interest in health psychology, we decided to explore the issue of undergraduate freshman lifestyle, particularly weight gain. ‘Freshers’ 15′ – the tendency for undergraduate students to gain approximately 15 lb (6.82 kg) in weight during first-year study – is an American concept. Although widely researched in the United States, we found little evidence of the UK study. The US studies' research design and methods varied considerably, so we intended not to replicate or conduct a comparative study but to conduct an exploratory study to establish whether there was evidence of this concept in a UK university sample. Owing to the multi-faceted nature of weight gain, including lifestyle choices and other factors, we took a classic mixed-methods approach, embracing the quantitative and qualitative methods that best fit our exploratory aim. This account of our mixed-method study focuses on design choices in respect of our chosen data-collection methods and how successfully they worked together to investigate students' lifestyle choices. Additional attention is paid to the benefits of a mixed-method approach, challenges encountered and the merits of triangulating data collection, including how interviewing was used to supplement the questionnaire and physiological data to allow further investigation of students' meaning and experiences regarding their lifestyle choices.