The effectiveness of a water intake challenge on beverage intake in Australian adults.

Part 1 of the study involved completing an initial screening survey. Participants were asked to complete a series of questions about their health behaviours (including diet and water intake) and their readiness to change such behaviours. They were also asked several behavioural and psychological measures that formed predictors for participation in the intervention (the second phase of the study). Participants who met the criteria for low daily water intake, namely, <1.2L of water per day based on previous research were invited to participate in the second phase of the study. They were asked to contact the study team to indicate their interest and provide their initials and last 3 digits of their phone number to facilitate data matching. Those who contacted the team were sent a second information sheet and asked to indicate consent via email. Part 1 occurred within a couple of weeks of part 2. Part 2: Participants that consented to take part in the 4-week health behaviour challenge were asked to increase their water intake to 8 (females) or 10 (males) cups a day. We defined a cup as 250mls. Participants were provided with an online visual tile explaining this challenge aim, which also stated that they could approach this goal any way that worked for them, but to focus on drinking plain water rather than other beverages containing water (e.g., cordial, tea). Participants used an Ecological Momentary Assessment (EMA) smartphone application to record their water and other beverage intake once daily as well as their mood twice daily. No other direct contact was made with the participants over the four weeks, other than to respond to enquiries and to send links to complete follow-up surveys (i.e., start of challenge, week 2, week 4). A key outcome of the study involved validating the CSIRO behaviour change readiness index, which comprised psychological and experiential predictors of initial interest and committed intention to change a health behaviour, as well as behaviour change success. This will be done by assessing the utility of the index for predicting successful short-term behaviour change outcomes in the dietary domain (i.e., water drinking), but also to better understand the associations and strengths of relevant factors to refine this tool into a succinct survey. Thus, the study focused on predicting behavioural outcomes rather than improving health behaviours. The validation of the index involved participants from part 1 of the study.