Enhancing the potential effects of text messages delivered via an m-health intervention to improve packing of healthy school lunchboxes.

Objective: The aim of the study was to assess the impact of different lunchbox messages on parents' intention to pack a healthy lunchbox.

Design: This study employed an experimental design.

Setting: A series of messages were developed to align with the six constructs of the Health Belief Model. Messages were also developed that were (and were not) personalised and varied based on the source of the information provided (university, school, dietitian and health promotion service). During a telephone survey, participants were read the content of each message and asked about their intention to pack a healthy lunchbox.

Participants: Parents of primary school-aged children were randomised to receive different messages to encourage the packing of healthy lunchboxes.

Results: The study was completed by 511 parents. Linear mixed regression analyses identified significant differences (P < 0·05) in intention scores between variant messages targeting the same behavioural constructs for 'susceptibility', 'severity', 'benefits' and 'barriers' but not 'cues to action' or 'self-efficacy'. The highest mean behavioural intention score was for 'benefits', whilst the lowest mean score was for 'barriers'. There were no significant differences in intention scores of parents receiving messages from a dietitian, university, health promotion team or school (P = 0·37). Intention scores did not differ in which messages were personalised based on child's name (P = 0·84) or grade level (P = 0·54).

Conclusions: The findings suggest that messages that focus on the benefits of packing healthy lunchboxes may be particularly useful in improving intentions of parents to pack healthy foods for their children to consume at school.