title: Longitudinal motivational predictors of dietary self-care and diabetes control in adults with newly diagnosed type 2 diabetes mellitus.
abstract: OBJECTIVE
  This prospective study examined relationships between constructs from social-cognitive theory (Bandura, 1986) and self-determination theory (Deci & Ryan, 1985; Deci & Ryan, 1991) and the diabetes outcomes of dietary self-care and diabetes control.
  
  
  METHODS
  Longitudinal data were collected from 237 people newly diagnosed with Type 2 diabetes who filled in questionnaires on dietary self-care, and motivational factors derived from social-cognitive theory and self-determination theory. Blood samples were taken to assess diabetes control (HbA1c). Repeated measurements were taken every 3-4 months for a total of five time points over 18 months. Predictor measures included autonomy support, autonomous and controlled motivation, amotivation, dietary self-efficacy, positive and negative outcome expectancies for dietary self-care and self-evaluation. Age, sex, BMI, and diabetes knowledge were included as control measures.
  
  
  RESULTS
  Using Generalized Estimating Equations (GEE) analyses two models were tested: a standard model reflecting longitudinal associations between absolute values of predicted and outcome variables; and a change model examining motivational predictors of changes over time in diabetes outcomes of dietary self-care and diabetes control (HbA1c). Dietary self-care was longitudinally associated with self-efficacy, self-evaluation (the strongest predictor) autonomy support and autonomous motivation, but not with controlled motivation or outcome expectancies. Changes in dietary self-care were predicted by changes in self-efficacy, self-evaluation, and controlled motivation but not by changes in autonomous motivation or autonomy support. Negative outcome expectancies regarding diet were longitudinally associated with HbA1c, and changes in negative outcome expectancies predicted changes in HbA1c. However, there were indications that dietary self-care predicted changes in HbA1c.
  
  
  CONCLUSIONS
  The results indicate that autonomy support, self-efficacy and, in particular, self-evaluation are key targets for interventions to improve dietary self-care.
authors.affiliation: School of Psychology, University of Birmingham.
authors.forename: Arie
authors.initials: A
authors.lastname: Nouwen
authors.affiliation: Staffordshire University.
authors.forename: Teri
authors.initials: T
authors.lastname: Ford
authors.affiliation: School of Psychology, University of Birmingham.
authors.forename: Andreea Teodora
authors.initials: AT
authors.lastname: Balan
authors.affiliation: Department of Epidemiology and Biostatistics, VU Medical Centre.
authors.forename: Jos
authors.initials: J
authors.lastname: Twisk
authors.affiliation: Community Health Sciences, School of Public Health, University of Illinois at Chicago.
authors.forename: Laurie
authors.initials: L
authors.lastname: Ruggiero
authors.affiliation: Department of Psychology and Mental Health, Staffordshire University.
authors.forename: David
authors.initials: D
authors.lastname: White
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003924:Diabetes Mellitus, Type 2 / Q000523:psychology* / Q000628:therapy; D059026:Diagnostic Self Evaluation; D004032:Diet; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009042:Motivation; D011446:Prospective Studies; D012648:Self Care / Q000523:psychology*; D012649:Self Concept; D011795:Surveys and Questionnaires