Stress and number of servings of fruit and vegetables consumed: Buffering effects of monetary incentives.

Diet is a key factor of human health, and additional research is needed in order to understand the psychological causes, consequences, and moderators of dietary behavior. Participants in two studies in the United States completed a 21-day intervention that involved either self-monitoring their fruit and vegetable consumption or self-monitoring combined with earning monetary incentives for behavior. Each day, participants reported their stress, affect, and consumption of fruits and vegetables. Hierarchical linear mixed effects model results suggest that on average, daily reports of higher stress were associated with fewer fruits and vegetables consumed on that day. This effect was moderated by incentive condition, such that the relationship between stress and fruit and vegetable consumption was reduced among incented participants. There was also a marginal negative effect of time on consumption of fruits and vegetables, but this was also significantly moderated by condition, such that those participants who did not receive incentives decreased their daily servings, while incented participants did not decrease over the course of the intervention. These studies suggest that incentives may be a novel method for buffering against the negative effect of daily stress on eating a healthy diet.