Social norms and financial incentives to promote employees' healthy food choices: A randomized controlled trial

Abstract

Objective: Population-level strategies to improve healthy food choices are needed for obesity prevention. We conducted a randomized controlled trial of 2672 employees at the Massachusetts General Hospital who were regular customers of the hospital cafeteria with all items labeled green (healthy), yellow (less healthy), or red (unhealthy) to determine if social norm (peer-comparison) feedback with or without financial incentives increased employees' healthy food choices.

Methods: Participants were randomized in 2012 to three arms: 1) monthly letter with social norm feedback about healthy food purchases, comparing employee to "all" and to "healthiest" customers (feedback-only); 2) monthly letter with social norm feedback plus small financial incentive for increasing green purchases (feedback-incentive); or 3) no contact (control). The main outcome was change in proportion of green-labeled purchases at the end of 3-month intervention. Post-hoc analyses examined linear trends.

Results: At baseline, the proportion of green-labeled purchases (50%) did not differ between arms. At the end of the 3-month intervention, the percentage increase in green-labeled purchases was larger in the feedback-incentive arm compared to control (2.2% vs. 0.1%, P=0.03), but the two intervention arms were not different. The rate of increase in green-labeled purchases was higher in both feedback-only (P=0.04) and feedback-incentive arms (P=0.004) compared to control. At the end of a 3-month wash-out, there were no differences between control and intervention arms.

Conclusions: Social norms plus small financial incentives increased employees' healthy food choices over the short-term. Future research will be needed to assess the impact of this relatively low-cost intervention on employees' food choices and weight over the long-term.

Trial registration: Clinical Trials.gov: NCT01604499.

Keywords: Financial incentives; Food choice; Obesity prevention; Social norms; Worksite.

Figure 1. Study flow diagram

This study took place at Massachusetts General Hospital in Boston, MA in 2012–2013.

Figure 2

Observed changes and linear trends in proportion of green-labeled (healthy) cafeteria purchases. Panel A: P=0.03 for feedback-incentive vs. control (end of intervention); P=0.07 for feedback-only vs. control (end of intervention); P>0.10 for both intervention groups compared to control (end of wash-out). Panel B: P=0.004 for linear trend of feedback-incentive vs. control and P=0.04 for linear trend of feedback-only vs. control during intervention period; P>0.10 for both comparisons during washout period. This study took place at Massachusetts General Hospital in Boston, MA in 2012–2013.

Figure 3

Change from baseline in green-labeled (healthy) purchases by employees from the least healthy and healthiest quartiles of cafeteria purchases. * P<0.05, adjusting for age, sex, race, job type, and part-time job status. ** P<0.01, adjusting for age, sex, race, job type, and part-time job status. All comparisons in with no footnote have P >0.10. This study took place at Massachusetts General Hospital in Boston, MA in 2012–2013.