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Figure 2. Theory of planned behaviour variables
predicted fruit and vegetable consumption at T2 beta weights shown, significant paths in dark blue
Fruit and vegetable
intake
T2
Intention
T2
Attitude
T2
Subjective norm
T2
Perceived behavioural
control
T2
Theory of planned behaviour cognitions do not
predict change in fruit and vegetable
consumption Emily Kothe & Barbara Mullan
School of Psychology, The University of Sydney, Australia
[email protected] & [email protected]
Background The present study investigated whether
theory of planned behaviour (TPB) cognitions
predicted change in fruit and vegetable intake in a trial
cohort of Australian young adults.
Methods Participants of a randomised controlled trial
of a TPB-based intervention (N=162) completed
questionnaires assessing fruit and vegetable intake
and TPB constructs at baseline and 30 days.
Findings The theory of planned behaviour predicted
fruit and vegetable consumption at baseline and
follow-up. Change in attitude, perceived behavioural
control and subjective norm predicted change in
intention, but change intention and perceived
behavioural control failed to predict change in fruit and
vegetable intake
Discussion Failure of the theory to predict behaviour
change may be due to the inadequacy of the theory or
to artefacts of the study design that facilitate change in
fruit and vegetable consumption without corresponding
changes in cognitions. Researchers should be
cautious when interpreting empirical support for the
predictive utility of the TPB as evidence the theory can
be applied to behaviour change.
Australian young adults are less likely than any other
age group to consume adequate quantities of fruit and
vegetables.1
The theory of planned behaviour has previously been
found to predict a large proportion of the variance in
intake in this population. 2,3,4
To determine whether change in fruit and vegetable
consumption in the FreshFacts study could be
explained by change in theory of planned behaviour
cognitions.
University undergraduates (N=162) completed a
theory of planned behaviour intervention designed to
increase fruit and vegetable intake.
Participants were randomised to either the intervention
or control conditions.
All participants completed a theory of planned
behaviour questionnaire and a self-report measure of
fruit and vegetable consumption at baseline and
immediate post-intervention follow-up (Day 30).
Abstract
Methods
Conclusion
References
Acknowledgments
Introduction
Objectives
Baseline assessment
(n=180)
Control
(n=90)
Follow-up assessment
(n=162)
Intervention
(n=90)
Results
Figure 1. Theory of planned behaviour variables
predicted fruit and vegetable consumption at T1 beta weights shown, significant paths in dark blue
Fruit and vegetable
intake
T1
Intention
T1
Attitude
T1
Subjective norm
T1
Perceived behavioural
control
T1
.18 .40
.37 .42
Change in fruit and
vegetable intake
Intention
Attitude change
Subjective norm
change
Perceived behavioural
control change
Figure 3. Change in theory of planned behaviour
variables did not predict change in fruit and vegetable
consumption beta weights shown, significant paths in dark blue
.03 .14
Results (cont).
Theory of planned behaviour accounted for 17% of
variance in fruit and vegetable intake at baseline.
Theory of planned behaviour accounted for 24% of
variance in fruit and vegetable intake at follow-up.
Theory of planned behaviour accounted for just 2.3%
of variance in change in fruit and vegetable
consumption.
Failure of the theory to predict change in fruit and
vegetable consumption may reflect artefacts of the
study design.
However, the lack of support for the theory of planned
behaviour when applied to the modelling of behaviour
change is consistent with a other recent intervention
studies based on the theory.5
Researchers should not assume that theories that
successfully predict behaviour (either crosssectionally
or prospectively) will adequately model change in
behaviour.
More research on the mediation of behaviour change
through theory relevant pathways are needed to
confirm or clarify these findings.
This research would not have been possible without
the support of staff and students at the University of
Sydney. The researchers would especially like to thank
Vanessa Allom, Kirby Sainsbury, Jemma Todd, Alyssa
Milton and Kristina Xavier.
1. Australian Bureau of Statistics. National Nutrition
Survey. Canberra 1997
2. Allom V, Mullan B. Self-regulation versus habit: The
influence of self-schema on fruit and vegetable
consumption. Psychology & Health. 2011.
3. Kothe EJ, Mullan B, Butow P. Promoting fruit and
vegetable consumption: Testing an intervention
based on the theory of planned behaviour. Appetite.
2012;58(3).
4. Collins A, Mullan B. An extension of the theory of
planned behavior to predict immediate hedonic
behaviors and distal benefit behaviors. Food
Quality and Preference. 2011;22(7).
5. Hardeman W, Kinmonth AL, Michie S, Sutton S.
Theory of planned behaviour cognitions do not
predict self reported or objective physical activity
levels or change in the ProActive trial. British
Journal of Health Psychology. 2011;16(1):135-50.
