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 0-100 (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 to 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 T2/T3 (p-interaction <0.001).

CONCLUSION: Compared to 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.