Health behaviours as predictors of the Mediterranean diet adherence: a decision tree approach

OBJECTIVE: This study aimed to identify health behaviours that determine adolescent’s adherence to the Mediterranean diet (MD) through a decision tree statistical approach. DESIGN: Cross-sectional study, with data collected through a self-fulfilment questionnaire with five sections: (1) eating habits; (2) adherence to the MD (KIDMED index); (3) physical activity; (4) health habits and (5) socio-demographic characteristics. Anthropometric and blood pressure data were collected by a trained research team. The Automatic Chi-square Interaction Detection (CHAID) method was used to identify health behaviours that contribute to a better adherence to the MD. SETTING: Eight public secondary schools, in Algarve, Portugal. PARTICIPANTS: Adolescents with ages between 15 and 19 years (n 325). RESULTS: According to the KIDMED index, we found a low adherence to MD in 9·0 % of the participants, an intermediate adherence in 45·5 % and a high adherence in 45·5 %. Participants that regularly have breakfast, eat vegetable soup, have a second piece of fruit/d, eat fresh or cooked vegetables 1 or more times a day, eat oleaginous fruits at least 2 to 3 times a week, and practice sports and leisure physical activities outside school show higher adherence to the MD (P < 0·001). CONCLUSIONS: The daily intake of two pieces of fruit and vegetables proved to be a determinant health behaviour for high adherence to MD. Strategies to promote the intake of these foods among adolescents must be developed and implemented.