Abstract
Perceptions of social norms around eating behavior can influence food choices. Communicating information about how others are changing their eating behavior over time (dynamic descriptive social norms) may motivate individuals to change their own food selection and consumption. Following a four-week baseline period, 22 in-store restaurants of a major retail chain across the UK were randomized to display a dynamic descriptive social norm message intended to motivate a shift from meat-to plant-based meals either during the first two, or last two weeks of the four-week study period. A linear regression model showed there was no evidence of an effect of the intervention (β = -0.022, p = .978, 95% CIs: −1.63, 1.58) on the percentage sales of meat- vs plant-based dishes. Fidelity checks indicated that adherence to the intervention procedure was often low, with inconsistencies in the placement and display of the intervention message. In four stores with high fidelity the estimated impact of the intervention was not materially different. The lack of apparent effectiveness of the intervention may reflect poor efficacy of the intervention or limitations in its implementation in a complex food purchasing environment. The challenges highlighted by this study should be considered in future design and evaluation of field trials in real-world settings.
Highlights
Meat consumption in the UK has increased from 69 kg to 79 kg per year per capita in the past fifty years, while meat production has almost doubled in the same timeframe from 2.2 to 4.1 million tons per year (Ritchie & Roser, 2017)
There were no significant differences in the mean percentage sales of plant-based meals between the restaurants allocated to the control first (M=.096, SD=.024, 95% CIs: 0.080, 0.112) and intervention first (M=.105, SD=.024, 95% CIs: 0.089, 0.121) arms in the four weeks before the study; (t(20) = -0.90, p = .376, Cohen’s d = -.386), suggesting the control and intervention stores were well matched in this respect
The inde pendent samples t-test returned no significant results between the intervention first (M = -.0003, SD=.01, 95% CIs: -.007, 0.006) and control first (M=.0018, SD = 0.14, 95% CIs: -.008, 0.011) conditions; (t (20) = -0.40, p = .690, Cohen’s d = .172) suggesting the analysis could proceed as a cross-over design
Summary
Meat consumption in the UK has increased from 69 kg to 79 kg per year per capita in the past fifty years, while meat production has almost doubled in the same timeframe from 2.2 to 4.1 million tons per year (Ritchie & Roser, 2017). It seems that this rise in meat con sumption peaked in the mid-2000s, with average daily meat consump tion per capita decreasing by 17% in a recent decade (Stewart, Piernas, Cook, & Jebb, 2021). Appealing to individuals’ perceptions of social norms around meat consumption, presents an oppor tunity to motivate a shift away from animal-based to plant-based foods
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