Author: Joyce Haddad
Haddad, Joyce, 2021 Communicating for impact: tailoring nutrition messages to influence dietary behaviour, Flinders University, College of Nursing and Health Sciences
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Poor diet quality is a factor associated with the prevalence of non-communicable diseases among Australian adults. To improve diet quality, brief online dietary feedback interventions have been developed, but, to date, have had modest effect. To enhance intervention effectiveness, a potential first step is identifying the dietary target that can maximise overall diet quality improvement. The second step can be making dietary feedback more influential by framing nutrition messages. Since the influence of differently framed nutrition messages may vary between individuals, tailoring the message frame may be more effective than using one generic message for everyone. Therefore, this thesis aimed to design and test a brief online dietary feedback intervention with tailored nutrition message frames and enhanced behavioural support, for improving Australian adults’ diet quality.
The thesis aim was addressed through four studies. First, a secondary dietary pattern subgroup analysis was used to identify the priority target. Next, a randomised controlled trial with a nested crossover trial was designed to test a brief online dietary feedback intervention: Shifting My Nutrition Score in 28 Days. The crossover trial tested the effectiveness of four nutrition message frames, using participants’ intention to change as the outcome. The messages were framed as positive, negative, majority or minority descriptive norm messages. The message associated with a participant’s highest intention was delivered as the tailored message. The randomised controlled trial tested whether a tailored nutrition message, with enhanced behavioural support, was more effective than a generic message used in standard practice, in influencing dietary behaviour. Last, participant characteristics as predictors of intervention effectiveness were analysed.
The secondary analysis showed that 81% of the sample (n = 216,045) did not comply with the Australian Dietary Guidelines for discretionary choices, regardless of population subgroup. Thus, this food group was chosen as the priority dietary target for intervention. The crossover trial revealed that nutrition message frames increased intention from baseline; however, the difference in effects between the message frames was limited. The Shifting My Nutrition Score in 28 Days intervention showed limited difference in the effect between the tailored and generic nutrition messages on discretionary choice intake. However, the intervention achieved a significant one serve reduction in discretionary choice intake (n = 1,441; η2 = 0.28, p < 0.001). Exploratory analysis revealed that having a lower diet quality at baseline was associated with a greater likelihood of a one serve or more reduction in discretionary choice intake (OR 1.57, 95% CI [1.47, 1.68], p < 0.001).
To the best of the PhD candidate’s knowledge, this is the first study to incorporate nutrition message frames, individually tailored to influence intention, into a novel, evidence-based, brief online dietary feedback intervention. The original contribution to knowledge of this thesis is that it may not be necessary to tailor nutrition message frames and provide enhanced behavioural support for improving the diet quality of a sample with high baseline intention. Extending this new knowledge may allow researchers to design and deliver other influential messages, within practical and effective tailored interventions, to continue improving Australian adults’ diet quality.
Keywords: health messaging, nutrition messaging, nutrition communication, dietary patterns, dietary pattern analysis, discretionary choices, eHealth, digital interventions, dietary behaviour, dietary behaviour change
Subject: Nutrition thesis
Thesis type: Doctor of Philosophy
Completed: 2021
School: College of Nursing and Health Sciences
Supervisor: Professor Rebecca Golley