A first limitation of this study is that we used student volunteers. We have to take into account that participants were probably interested in this topic, which might have resulted in a selection bias. However, sample characteristics showed sufficient variety in BMI and perceived health status. Secondly, whereas we might expect differences in behaviours according to gender or year in school, we chose to use mixed-gender focus groups including students of different study years and disciplines, allowing us to create interaction between both genders with a variety of study experience and backgrounds, which in turn generated a greater diversity in opinion within each focus group. Thirdly, focus groups were conducted at one university, which has a campus outside the city centre. Because of university specific environmental differences