Monitoring a meat-free pledge with smartphones: An experimental study.

Pledges are a popular strategy to encourage meat reduction, though experimental studies of their efficacy are lacking. Three-hundred and twenty-five participants from three different countries (UK, Germany, Australia) were randomly assigned to pledge 28 days meat-free or not, and their behavior was tracked via smartphones. Participants answered daily surveys regarding their eating behavior, meat cravings, and shared photos of their meals. Baseline data was collected prior to the pledge, after the 28 days, and one-month post-intervention. Participants assigned to the pledge condition ate less meat across the 28 days, compared to control participants. Meat reductions, observed at outtake, did not endure one-month post-intervention. Overall, German participants ate the least amount of meat, and showed the sharpest decrease in consumption when pledging. Meat cravings tended to increase among pledgers, relative to control participants. Pledgers who reported high starting intentions and conflict about meat tended to eat less meat and reported fewer cravings. All participants reported reduced meat-eating justifications one-month post-intervention. These findings provide experimental evidence that pledges can encourage meat consumers to reduce their intake, though additional mechanisms are needed to sustain commitments.