Psychosocial Influences on Fruit and Vegetable Intake Following a NYC Supermarket Discount

Abstract

Objective: To assess the effect of a 50% discount on fruits and vegetables (F&V) on the purchase and intake of F&V and on psychosocial determinants of F&V intake: self-efficacy (SE), stages of change (SOC), and perceived barriers (PB).

Methods: This randomized controlled trial was conducted in local supermarkets over 16 weeks, including a 4-week baseline, 8-week discount intervention, and 4-week follow-up. Shoppers with overweight or obesity (BMI > 25) were randomized to receive a discount or no discount via their reward scan card after the baseline. Twenty-four-hour recalls and psychosocial measures were obtained for each study period.

Results: Purchases (P < 0.0005) and intakes (P = 0.019) of F&V increased significantly during the intervention, while only F&V intake was sustained at follow-up. The discount intervention increased SE (P < 0.01) and SOC (P < 0.05) and did not decrease PB (P = 0.057) during the intervention. SOC mediated the discount intervention effect on F&V intake (P < 0.05) during the intervention, explaining 43% of variance.

Conclusions: A supermarket discount intervention led to increases in purchases and intakes of F&V and increases in the psychosocial factors SE and SOC and did not decrease PB. The discount intervention prompted participants to move from the preparation to action stage of SOC, which acted as a mediator for increased F&V intake.

Trial registration: ClinicalTrials.gov NCT01509664.

Conflict of interest statement

The authors declared no conflict of interest.

© 2017 The Obesity Society.

Figures

Figure 1

Study procedures conducted at various assessment time points over the three study time periods. *IC refers to initial consultation.

Figure 2

Consolidated Standards of Reporting Trials flow diagram for participant enrollment, intervention allocation, follow-up, and data analysis.

Figure 3

Gross (price before discounts) weekly purchasing of discounted fruits and vegetables during baseline, intervention, and follow-up periods. The discount group increased purchasing during the intervention period (P

Figure 4

Fruit and vegetable intake during baseline, intervention, and follow-up periods. Fruit and vegetable intake increased (p=0.019) during the intervention period in the discount group relative to the control group and was sustained during the follow up period (P=0.003). (mean ± 1 standard error of the mean).

Figure 5

Basic multiple mediator model of psychosocial outcome measures at end of intervention on F&V intake. Error terms for all outcome measures were included in the analysis but omitted in this figure. Values are β values, p-values

Figure 6

Final model showing significant mediation effect of stage of change (SOC) at end of intervention on F&V intake. Error terms for all outcome measures were included in the analysis but omitted in this figure. Values are β values, p-values