Background: The aim of this study is to explore the psychometric properties of the Motiva.Diaf questionnaire, which assesses the adherence to healthy diet and physical activity in clinical patients.
Method: Participants were 230 patients, who attended hospital services, with a mean age of 49.28 years (SD = 12.34). Women constituted 55.7% of the patients. Two weeks after initial administration, 40 participants, from those who had another hospital appointment scheduled, were selected at random to complete again the questionnaire in order to assess test–retest reliability. Results: the accuracy of the scores is adequate both in terms of internal consistency (α = .802; Ω = .776) and temporal stability ( r = .786). The test’s structure is essentially one-dimensional, and the scores in this dimension converge with other necessary basic psychological measurements ( r Diet = .294; r Physical Activity = .359) and perceived health ( r = .266). In addition, a relatively moderate relationship was found with the Body Mass Index ( r = - .129).
Conclusions: The test has shown adequate reliability and validity for evaluating adherence to healthy habits. The availability of an instrument with these characteristics has significant implications for evaluating behaviour, designing and implementing behavioural interventions.