What is the impact of increasing the prominence of calorie labelling? A stepped wedge randomised controlled pilot trial in worksite cafeterias

Abstract

Background: Calorie labelling may help to reduce energy consumption, but few well-controlled experimental studies have been conducted in real world settings. In a previous randomised controlled pilot trial we did not observe an effect of calorie labelling on energy purchased in worksite cafeterias. In the present study we sought to enhance the effect by making the labels more prominent, and to address the operational challenges reported previously by worksites.

Methods: Three worksite cafeterias were randomised in a stepped wedge design to start the intervention at one of three fortnightly periods between March and July 2018. The intervention comprised introducing prominent calorie labelling for all cafeteria products for which calorie information was available (on average 87% of products offered across the three sites were labelled). Calorie content was displayed in bold capitalised Verdana typeface with a minimum font size of 14 e.g.120 CALORIES. Feasibility and acceptability were assessed using post-intervention surveys with cafeteria patrons and semi-structured interviews with managers. Effectiveness was assessed using total daily energy (kcal) purchased from intervention items across the three sites, analysed using semi-parametric GAMLSS models.

Results: Recruitment and retention of worksite cafeterias proved feasible: all three randomised sites successfully completed the study. Post-intervention feedback suggested high levels of intervention acceptability: 87% of responding patrons wanted calorie labelling to remain in place. No effect of the intervention on daily energy purchased was observed: -0.6% (95%CI -2.5 to 1.2, p = .487). By-site analyses showed similar null effects at each of the three sites, all ps > .110.

Conclusions: There was no evidence that prominent calorie labelling changed daily energy purchased across three English-based worksite cafeterias. The intervention was feasible to implement and acceptable to patrons and managers.

Keywords: Calorie labelling; Choice architecture; Nudging; Randomised controlled trial; Stepped wedge trial; Workplace interventions.

Fig. 1

CONSORT diagram of participant flow through the study.

Fig. 2

A graphical presentation of the study's stepped wedge design.

Fig. 3

Examples of calorie labelling: a) on a product; b) along shelf-edging; c) on a tent card; and d) on a menu.

Fig. 4

Total energy sold per day for intervention items across the three sites with information displayed for day of the week.

Fig. 5

Transactions per day for intervention items across the three sites with information displayed for day of the week.