Prescribing vegetarian or flexitarian diets leads to sustained reduction in meat intake

Abstract

Many people agree that reducing the consumption of meat has good ends (e.g., for animal welfare, the environment, and human health). However, the question of which advocacy strategies are most effective in enabling wide-spread meat reduction remains open. We explored this by prescribing four different meat reduction diets to omnivorous participants for a seven-day adherence period, and studied their meat consumption over time. The diets included a Vegetarian diet, and three flexitarian diets (Climatarian – limit beef and lamb consumption; One Step for Animals – eliminate chicken consumption; Reducetarian – reduce all meat consumption). Results showed pronounced differences between groups in meat consumption during the adherence period, where the Vegetarian group ate significantly less meat than the flexitarian groups. All groups decreased their meat intake in the weeks following the adherence period compared to baseline, however, there were no significant group differences in the level of decrease over time. Participants also changed their attitudes toward meat and animals from pre-to post-intervention, and decreases in commitment toward and rationalization of meat-eating partially mediated change in meat intake. These findings reveal that the diet assignments had some impact on participants’ meat consumption and attitudes even after the prescribed adherence period had ended. However, the sustained decrease in consumption did not vary depending on what meat reduction strategy was originally used.

Introduction

The consumption of meat has been a large part of human life throughout our evolutionary history. However, there are compelling ethical and health-related reasons for reducing meat consumption (e.g., Singer, 1975/2009), and transitioning from meat to plant-based eating has seen growing momentum (Roy Morgan Research Institute, 2016; The Vegetarian Resource Group, 2020). Meat reduction advocacy strategies vary in the degree of meat reduction called for (e.g., decreasing versus eliminating meat consumption), and in the type of meat to abstain from (e.g., red meat versus meat from chickens). While there are rationales supporting various meat reduction approaches, the question of which rationales and advocacy strategies are most effective in broadly reducing meat consumption remains open.

A well-known approach to reducing meat consumption is vegetarianism (i.e., adopting a meat-free diet). While a vegetarian diet leads to the least meat-eating by definition, many people perceive this diet as difficult to adopt and maintain (e.g., Corrin & Papadopoulos, 2017; Mullee et al., 2017; Pohjolainen et al., 2015). As a result, several advocacy groups alternatively promote flexitarian diets, where meat consumption is reduced in some significant way without being eliminated completely (Rosenfeld, 2018). Because reducing meat consumption is easier than eliminating it, flexitarian diets may be more readily adopted, and so advocating flexitarian approaches may enable significant population-level decreases in meat consumption (Spencer et al., 2018). In the present study, we asked a sample of omnivorous participants to spontaneously adopt a meat reduction diet (including a vegetarian diet and three different flexitarian diets), and examined how the rationales for and conditions of each diet affected participants’ meat consumption over time.

Meat is a highly valued food source across the globe (Ritchie & Roser, 2020) due to it being tasty (Piazza et al., 2015), a source of nutrition (Roser & Ritchie, 2020), and implicated in cultural rituals (Leroy & Praet, 2015). Yet despite the esteemed place meat has as a food source, an increasing number of people intentionally reduce or eliminate meat from their diets (e.g., The Vegetarian Resource Group, 2020). The motivation to reduce meat intake is generally driven by ethical concerns for animal welfare and environment impact, as well as concern for human health (Rosenfeld, 2018; Ruby, 2012). Given that ethics-based arguments for reducing meat can be particularly impactful (Berndsen & van der Pligt, 2005; Palomo-Vélez et al., 2018), the present study's rationales were built around the two primary ethical concerns that drive meat reduction: animal welfare and environmental concern.

Perhaps the best-known argument against meat consumption relates to the amount of animal suffering that is endemic to meat industry practices (Singer, 1975/2009). Animal welfare is a commonly cited reason for eliminating or at least reducing meat consumption (Rosenfeld, 2018), and underpins the approach of many animal activist groups (e.g., People for the Ethical Treatment of Animals (PETA), Animals Australia, Humane Society, Animal Justice Project, and the Animal Liberation Front).

A second substantial motivation for reducing the production and consumption of meat is the associated environmental consequences. Consuming meat adversely affects the environment due to the production of greenhouse gases that results from rearing certain kinds of animals for meat (Macdiarmid et al., 2016), particularly ruminant animals (e.g., cows; Eshel et al., 2019). Scientific models show that reducing the production and consumption of meat (particularly ruminant meat) is indispensable for reducing greenhouse gas emissions and mitigating the impact of climate change on the environment (Hedenus et al., 2014). Although the issue of environmental harm has received less attention within campaigns to reduce meat consumption, it has been the primary focus of some advocacy organizations (e.g., Less Meat Less Heat).

The varying reasons to reduce meat intake creates different recommendations regarding how people should alter their meat consumption. This may include differences in both the type of meat that people are recommended to avoid (e.g., ruminant versus poultry meat), as well as the amount of meat that is acceptable for consumption.

Since meat is only produced if it is consumed, a well-known step individuals take to reduce the production of meat is the adoption of a vegetarian diet (Singer, 1975/2009) – defined as complete abstention from meat products. However, an alternative approach to vegetarianism that is growing in popularity involves adopting a flexitarian diet. Flexitarian diets involve limiting meat intake without abstaining from meat completely (Rosenfeld et al., 2019). While vegetarianism can be perceived as difficult to adopt and maintain (e.g., Corrin & Papadopoulos, 2017; Mullee et al., 2017; Pohjolainen et al., 2015), flexitarian diets have been advertised as “easy” (Raphaely & Marinova, 2014; “One Step Australia,” 2018), and a “smaller ask” (One Step for Animals, n.d.) requiring less effort and commitment. This is reflected by the fact that a greater number of people worldwide subscribe to a flexitarian diet compared to vegetarianism (Ipsos, 2018).

There are various approaches to flexitarianism (Derbyshire, 2017). Certain advocacy groups emphasize the reduction of certain meat types over others depending on their chief ethical concern. For example, the One Step for Animals (OSFA) group has an animal welfare-based approach that calls only for abstention from eating chicken. This allows for a balance between i) reducing the number of animal lives taken in the meat industry with ii) what is feasible for consumers who struggle to abstain from meat entirely. In contrast to OSFA, the Climatarian diet is driven by environmental concern, which advocates limiting consumption of beef and lamb to one standard serving per week due to the pronounced impact of red meat production on the climate (Eshel et al., 2019). A third flexitarian diet comes from the Reducetarian advocacy group. Rather than having a rationale focusing on particular types of meat, Reducetarians advocate for significantly reducing the consumption of all meat types (e.g., by 50% of one's usual intake) to significantly mitigate the impact of meat consumption on animal welfare, the environment and on human health.

Together, these three flexitarian diets (OSFA, Climatarian, and Reducetarian) exist as alternatives to traditional vegetarianism that are described as “easy”, “achievable for the community” (Less Meat Less Heat, n.d.) and allowing for “manageable and actionable goals” (Reducetarian foundation, n.d.¹). While the aims of some groups focus on reducing specific meat types (OSFA and Climatarian), they all pose alternate strategies to promote wide-ranging reduction in meat consumption. The existence of various rationales and approaches for meat reduction leads to the consideration of which advocacy strategies actually prove most efficacious in persuading omnivores to reduce their meat intake. This question has been explored in some recent empirical work.

A growing literature has explored interventions for significantly reducing people's meat consumption or intention to consume meat (e.g., Camp & Lawrence, 2019; De Groeve et al., 2019; Garnett et al.., 2019; see Bianchi et al., 2018 and Harguess et al., 2020 for reviews). A number of these interventions have focused on heath-based reasons for meat reduction, and attempted to decrease the consumption of red or processed meat in particular (Carfora et al, 2017a, 2017b; Derbyshire, 2017; Klöckner & Ofstad, 2017; Wolstenholme et al., 2020). However, others have tested and found that ethics-based rationales around the environment or animal welfare can affect people's attitudes towards meat in general (Berndsen & van der Pligt, 2005; Cordts et al., 2014; Graham & Abrahamse, 2017; Loy et al., 2016).

While these previous approaches on ethics-motivated meat reduction have indicated useful strategies, there are limitations to this existing work. First, the majority of previous interventions have focused on methods for decreasing omnivores' intentions to eat meat. Very few studies have explored which interventions are effective in reducing the actual consumption of meat – with the exception of work that has focused on decreasing red meat consumption in particular (Carfora et al, 2017a, 2017b; Klöckner & Ofstad, 2017; Wolstenholme et al., 2020). Given that there can be a significant gap between people's reported intention to decrease meat intake with their actual behavior (Loy et al., 2016), it is important to study what interventions are truly effective in decreasing meat intake. Second, while some work has shown interventions can have an acute effect in reducing favorable attitudes towards meat, there is a dire need for longitudinal studies exploring whether interventions can have lasting effects on reducing meat intake (Bianchi et al., 2018; Graça et al., 2019). Finally, although some work has compared the efficacy of different rationales in reducing meat intake (e.g., health versus environmental; Palomo-Vélez et al., 2018; Wolstenholme et al., 2020), the efficacy of animal welfare-based advocacy is underexamined (Bianchi et al., 2018), and vegetarian versus flexitarian advocacy has only just started to be explored empirically.

A recent report by Faunalytics (Anderson, 2020)² tested the varying efficacy of vegetarian versus flexitarian advocacy on decreasing meat consumption. The authors did not find that exposing participants to either vegetarian or flexitarian advocacy reduced meat consumption compared to control groups. However, those shown the flexitarian message generally indicated openness to becoming flexitarian, while those shown the vegetarian message were generally reluctant to pledge to become vegetarian. This pledge decision partially mediated the effect of advocacy on meat consumption, where those seeing the vegetarian message were ironically less likely to order a meatless meal (18.9%) than the flexitarian group (25.8%).

The findings of the Faunalytics study reveal that some vegetarian advocacy approaches may be ineffective in persuading meat eaters to forego meat. Forcing vegetarian advocacy and difficult dietary decisions (i.e., pledging to go vegetarian) may lead to reactance in participants (where meat eaters react defensively to vegetarians or kinds of vegetarian advocacy; Bastian, 2019; Piazza et al., 2015; Rothgerber, 2014). On the other hand, milder meat reduction approaches may be relatively more palatable to omnivores and have a more positive impact.

Previous work has examined various strategies and rationales for decreasing how much people favor meat. However, the question of what kind of approach (vegetarian versus flexitarian) and type of ethical message (environmental versus animal welfare) is most impactful on meat consumption and attitudes over time is currently unknown. Further, while previous studies have tested the impact of information-based rationales on meat reduction (Bianchi et al., 2018), no work has explored how prescribing established meat reduction diets affects omnivores' meat intake. We set out to explore this using a robust longitudinal design, and included a vegetarian and variety of flexitarian-based advocacy approaches for comparison. In addition to meat intake, we also measured participants attitudes toward meat-eating and animals both pre- and post-intervention, and tested whether changes in these attitudes mediated change in meat intake over time. Specifically, the present study sought to examine the relative and absolute effects that prescribing four different meat reduction diets (a vegetarian diet, and three flexitarian diets) has on participants meat consumption and attitudes over time. We employed a novel design where we presented participants with the rationale for a specific meat reduction diet, asked them to commit to the diet for a seven-day ‘diet adherence’ period, and measured their meat consumption and attitudes, before, during, and after the adherence period.