Social connections and the healthfulness of food choices in an employee population

Abstract

Unhealthy food choice is an important driver of obesity, but research examining the relationship of food choices and social influence has been limited. We sought to assess associations in the healthfulness of workplace food choices among a large population of diverse employees whose food-related social connections were identified using passively collected data in a validated model. Data were drawn from 3 million encounters where pairs of employees made purchases together in 2015-2016. The healthfulness of food items was defined by 'traffic light' labels. Cross-sectional simultaneously autoregressive models revealed that proportions of both healthy and unhealthy items purchased were positively associated between connected employees. Longitudinal generalized estimating equation models also found positive associations between an employee's current food purchase and the most recent previous food purchase a coworker made together with the employee. These data indicate that workplace interventions to promote healthy eating and reduce obesity should test peer-based strategies.

Figure 1.. Properties of the predictive model for identifying social ties using cafeteria transaction and human resources data.

(a) Sensitivity/specificity trade-off; (b) Positive predictive value by probability cut-off; (c) Distribution of estimated tie probabilities. n = 1,054 for panels a and b. n = 2,974,388 dyads for panel c.

Figure 2.. Yearly associations between employee and co-worker purchases.

Coefficients (ρ) and 99% confidence intervals from simultaneously autoregressive models assessing associations between the healthfulness of employee and co-workers’ purchases of healthy and unhealthy foods and beverages over one-year cross-sections of time, adjusting for employee characteristics. Green- and red-labeled foods, 2015, n=5,934; green- and red-labeled foods, 2016, n=5,929; green- and red-labeled beverages, 2015, n=5,550; green- and red-labeled beverages, 2016, n=5,492 (Supplementary Tables 2 and 3).

Figure 3.. Prospective associations between employee’ current and co-worker’s prior purchase.

Coefficients and 99% confidence intervals of generalized estimating equations assessing the relationship between the healthfulness of co-workers’ purchases and employees’ subsequent purchases over 2015–2016, adjusting for employee, co-worker, and dyad characteristics, stratified by tie probability thresholds defining dyads. Higher tie probabilities indicate greater confidence in inferred social ties. Sample sizes decreased with increasingly restrictive tie probability thresholds (all-tie model through ≥0.6). They were n=6,382 and n=1,441 for foods and n=5,642 and n=1,138 for beverages, respectively (Supplementary Tables 5 and 6).