Effects of previous fruit intake, descriptive majority norms, and message framing on fruit intake intentions and behaviours in Dutch adults across a 1-week period

Objective
To test the effects of descriptive norm and message framing on fruit intake (intentions) in Dutch adults.

Design
Randomized pretest-posttest study using a 2 × 2 design.

Setting
Internet-based.

Participants
Dutch adults recruited via leaflets and announcements on intranet and Internet and who provided immediate intention (n = 294) and 1-week follow-up intention and fruit intake data (n = 177).

Intervention
Messages combining information on intake of others (low vs high intake) with information about positive or negative outcomes of (in)sufficient fruit intake.

Main outcome measures
Fruit intake intentions and fruit intake.

Analysis
Analyses of covariance.

Results
Those already consuming sufficient fruit and receiving negative information about insufficient fruit intake increased their motivation to consume sufficient fruit immediately (P = .03), but not at 1-week follow-up. Those who read positive information about sufficient fruit intake reported higher fruit consumption than those who read negative information about insufficient fruit intake (P = .03). This was stronger in those already consuming sufficient fruit. There were no effects of descriptive norm information (P > .19).

Conclusions and Implications
Information about outcomes was more persuasive than descriptive majority norm information. Effects were generally stronger in those already consuming sufficient fruit.