Fruit & vegetable intake amongst men in New Zealand : an evaluation and extension of a stage and continuous model of dietary behaviour : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Psychology at Massey University, Palmerston North, New Zealand
Purpose. The purpose of the study is to develop a better understanding of the process
of behaviour change and factors which contribute to an increased level of fruit and
vegetable intake (F&V) among men in New Zealand. The study aims to determine
the impact of psychosocial and contextual factors integrated into an extended stage
model. As a more parsimonious continuous model maybe sufficient for
understanding F&V intake, the study also plans to evaluate the impact of psychosocial
and contextual factors on behaviour, and whether intentions is the mechanism by
which the psychosocial factors influence behaviour.
Design. Data was collected using a self administered questionnaire in a mail survey
from N = 518 men aged 18 years and over randomly selected from the electoral roll.
Mean differences in factors across the stages of change were assessed with one way
ANOVAs and Games Howell post hoc tests, and trend analyses assessed linear and
non-linear components of trend. The independent impact of factors on intentions and
behaviour was assessed with hierarchical multiple regression analyses.
Measures. Stage of change was assessed with a single item measure, F&V intake
with a 7-item food frequency questionnaire, and food insecurity with items used in the
1997 National Nutrition Survey. Previously developed measures were used to assess
the pros, cons, self efficacy, self identity, and susceptibility to disease. Scales were
developed and adapted for F&V intake for control, descriptive and subjective norms.
Results. In total, 51% of men were in the action/maintenance stage and 32%, 10%
and 7% in the precontemplation, contemplation, and preparation stages respectively.
Mean F&V intake was 3.92 (SD = 2.08) servings a day and 30.4% were eating at least
5 servings. All factors differed significantly across the stages of change. The
predictor variables collectively explained R² = 43% (42% adjusted) in intentions and
40% (38% adjusted) in behaviour. The impact of self efficacy and intentions on
behaviour depended in part on household food insecurity status.
Discussion. Similar conclusions were reached using the stage and continuous model.
To increase intentions of eating 5 or more servings of F&Vs a day in the future,
interventions should modify perceived norms, self efficacy, pros and cons, and
awareness of F&V guidelines. Interventions targeting those with high food insecurity
may also be required to help translate their intentions into action.