Employees' Baseline Food Choices and the Effect of a Workplace Intervention to Promote Healthy Eating: Secondary Analysis of the ChooseWell 365 Randomized Controlled Trial

Background: Little is known about whether the effectiveness of workplace wellness programs differs by employees' baseline health behaviors.

Objective: This study examined the association of baseline cafeteria food choices with the effect of a workplace intervention on cafeteria food choices, dietary quality, and body mass index (BMI).

Design: This was a secondary analysis of the ChooseWell 365 randomized controlled trial, testing a set of behavioral interventions to improve diet and prevent weight gain.

Participants/setting: Participants were 602 employees of a Boston, MA, hospital who had purchased food from cafeterias, which used traffic-light food labeling. Data were collected in 2016-2020.

Intervention: The 12-month intervention (plus 12 months' follow-up) involved financial incentives and personalized feedback on cafeteria purchases. The control group received monthly letters with generic healthy eating and exercise tips.

Main outcome measures: Healthy purchasing scores (HPS) were calculated by weighting color categories (red = 0, yellow = 0.5, green = 1) and scaling from 0 to 100 (healthiest); employees were categorized into baseline (pre-intervention) HPS tertiles (T1 = least healthy, T3 = healthiest). Healthy eating index (HEI-2015) scores were calculated from two 24-hour dietary recalls. Intervention effects on 12- and 24-month changes in HPS (primary outcome), HEI-2015 score, and BMI were compared among tertiles. Subgroup analyses examined whether changes by tertile varied with financial rewards received.

Statistical analyses: Adjusting for baseline characteristics, multivariable linear regression assessed intervention effects across baseline HPS tertiles.

Results: Compared with T3, T1 employees had lower education; higher obesity, hypertension, and pre-diabetes; and lower HEI-2015 scores. The intervention increased HPS, but no change was observed in HEI-2015 scores or BMI; the intervention effect did not differ among tertiles at 12 or 24 months. Financial incentives were associated with a larger effect on 12-month HPS changes for T1 than for T2/T3 (P-interaction < 0.001).

Conclusion: Compared with employees with healthier baseline food choices, employees with the least healthy food choices and highest cardiometabolic risk had similar improvements in the nutritional quality of cafeteria purchases as a result of the behavioral intervention, and they appeared to be more responsive to financial incentives.