Defining and measuring stages of change for dietary behaviors: readiness to meet fruit, vegetable, and grain guidelines among Chinese Singaporeans.J Am Diet Assoc. 2000 Aug; 100(8):898-904.JA
To assess the ability of 2 algorithms to classify people by stage of change for consuming the recommended servings of grains (cereal foods) and total fruit and vegetables.
Assessment of stage involved an objective behavioral measure in the form of a self-administered food frequency questionnaire, followed by a brief telephone interview to assess intentions of subjects to increase intake to meet the recommended servings. Validity of the stage classification was assessed by comparison with three 24-hour dietary recalls.
One hundred and one Singaporean Chinese subjects (mean age = 38.7; 51% men) were recruited from 716 respondents who had taken part in a survey investigating factors influencing consumption of grains, fruit, and vegetables.
STATISTICAL ANALYSES PERFORMED
Differences in mean intake by diet recalls across the stages were investigated using analysis of variance. Sensitivity, specificity, and predictive values of the algorithms were also determined.
There were significant increases across the stages in mean intake of grains (men: F(2,48) = 20.30, P < .001; women: F(2,47) = 23.39, P < .0001), and total fruit and vegetables (men: F(2,48) = 30.29, P < .005; women: F(2,47) = 37.29, P < .0001). Based on diet recalls for grains intake, the algorithms classified 89% of subjects having inadequate intakes into the preaction stages, and 75% of those having adequate intakes into the action or maintenance stages. For fruit and vegetables, 93% of subjects having inadequate intakes were classified into the preaction stages, and 76% of those having adequate intakes were classified into the action or maintenance stages.
Algorithms developed to assess stages of change for food-based rather than nutrient goals, and which include an objective assessment of intake, appear to improve the accuracy of stage classifications.