Randomised controlled trial of an online dietary feedback intervention targeting discretionary choice intake

This randomized controlled trial evaluated whether tailoring dietary feedback messages based on intention ratings, combined with behaviour change techniques (BCTs), could reduce discretionary choice intake (energy-dense, nutrient-poor foods and beverages). A total of 3,453 adults enrolled online, and 1,441 completed the follow-up surveys. Participants were randomised to receive either two emails with tailored nutrition message frames and enhanced behavioural support (delivered through nine embedded BCTs, such as goal setting and action planning), or two emails with generic nutrition messages without additional support. The primary outcome was daily servings of discretionary choices, and secondary outcomes included predictors of intake reduction. No significant difference in discretionary choice intake was observed between the groups (3.2 ± 0.13 vs. 3.1 ± 0.12 servings, p = 0.49). However, lower baseline diet quality was a significant predictor of a one serving or more reduction in discretionary choice intake (OR 1.57, 95% CI [1.47, 1.68], p < 0.001). To our knowledge, this is the first RCT to test multiple message frames simultaneously. The findings suggest that tailoring message framing based on intention, even when combined with established BCTs, may not enhance dietary outcomes in motivated populations. Future interventions may be more effective in populations with lower baseline intention and poorer diet quality.