5 Questions: Maya Mathur on encouraging people to eat less meat

Giving people information about animal welfare can motivate them to eat less meat, a meta-analysis of 100 studies has found.

- By Erin Digitale

Maya Mathur

Because eating less meat can benefit human health and the planet, Stanford statistician Maya Mathur, PhD, decided to assess what we know about motivating people to reduce their meat consumption.

“I see this as one of the rare things one can study that is at the nexus of quite a few social issues,” Mathur said. Meat-heavy diets are linked to diseases such as cancer, heart disease, stroke and obesity. In addition, animal agriculture contributes to greenhouse gas emissions and climate change, which in turn have harmful health effects.

Mathur’s team recently published a meta-analysis to evaluate studies that gave people information about animal welfare in meat production. They found that providing such information can motivate people to consume less meat. Mathur spoke with science writer Erin Digitale about the new research, which was published online May 11 in Appetite.

1. One concept I found intriguing in your paper is the “meat paradox.” What is it, and how is it useful in motivating people to reduce their meat consumption?

Mathur: The meat paradox is the idea that, by and large, people say and demonstrate that they like animals and are concerned about them, yet a large majority of people in developed countries eat a significant amount of animal products. While they say they oppose factory farming on ethical grounds, they support that industry financially through their purchases.

It’s a mismatch of people’s values and their behaviors. There are a number of reasons this happens. One is, largely due to efforts of the meat industry, we’re kept quite separate from the food we eat. We don’t really see what happens behind the scenes to get that chicken on the table.

Some of the interventions we studied try to make people aware of this paradox. For instance, one intervention consisted of showing people a photo of a lamb, along with a lamb chop, reminding them this food came from an animal.

2. Anecdotally, a common reason for people to become vegetarian is that they have concerns about how animals raised for food are treated. But your paper points out that animal welfare hasn’t received much attention in scientific studies intended to change meat consumption. Why not?

Mathur: It’s a very interesting question. I think one reason may be that we academics focus on interventions that line up with our own reasons for studying the problem. We write papers framing motivation for eating less meat in terms of health and environmental impacts, which are very useful motivations, though not the only reasons one might decide to eat less meat.

But we rarely see, outside of scholarly philosophy literature, discussion of the animal welfare side. It seems like there’s a disconnect: The public care about this issue, and there is lots of resulting research coming out of animal welfare-focused nonprofits, but that approach hasn’t reached academia as much.

3. Your recent meta-analysis looked at several studies that gave people information about animal welfare to try to lower their meat consumption. What did you learn?

Mathur: We did a comprehensive search of academic literature and of studies conducted by nonprofits, published outside of academic literature. We looked specifically for studies with any kind of animal welfare-related intervention and some kind of control condition. We found 100 studies that fit those criteria from 34 different articles, then collected statistical information about how strong the effect of that intervention was, and aggregated all the findings with our meta-analysis.

We don’t really see what happens behind the scenes to get that chicken on the table.

We found that the interventions consistently worked in the sense of reducing meat consumption, meat purchases or people’s intention to do those things. On average, the interventions produced a 22% increase in participants’ probability of eating less meat, compared with participants in the control arms of the studies.

Another interesting finding was that the effects of these interventions were pretty consistently beneficial and large enough to care about: around 71% of the interventions produced at least a 10% reduction in likely meat consumption. Relatively few effects were in the unintended direction. It doesn’t seem to be the case that these interventions backfire, whereas you could imagine that people feel that the interventions are moralizing or annoying, but that wasn’t what we found.

4. Some experts advocate encouraging people to eat less meat but not necessarily pushing them to become vegetarian or vegan. What are your thoughts about that from a research perspective?

Mathur: That raises two interesting questions: One is, What would be the optimal thing for people to do, regardless of how hard it is to actually make that behavioral change?

To examine this, it’s worth considering the difference between one person going from one meat meal a week to zero, versus one person going from seven meat meals a week to six. Although the first person’s change of going vegetarian seems so much more dramatic, the actual impact on society is exactly the same: It’s eliminating one meal of meat per week. The goal of these interventions shouldn’t necessarily be about having a tiny fraction of people cut animal products from their diets entirely. If everyone were to cut back just a little, that’s potentially as effective as a small number of people going cold turkey.

The second question is, What should interventions say to be effective? In other words, what should we ask people to do? If we ask people to eliminate meat entirely, we could imagine we might get a door-in-the-face effect — it might put people off. Maybe it’s better to ask people to reduce or cut one type of meat from their diets.

We looked at this by comparing interventions that asked people to go vegan or vegetarian or to reduce meat consumption, versus those that didn’t make a specific recommendation. Interestingly, it did not seem to be the case that the more forceful recommendations worked worse. If anything, it seemed like they worked a little better.

But these are comparisons across studies; they’re not randomized comparisons. I think a really important direction for future research is to conduct trials that consist of head-to-head, randomized comparisons of different tactics encouraging less meat consumption.

5. What other big questions do you want to tackle?

Mathur: It’s important to use stronger study designs to look at existing interventions. The studies we found showed consistently good effects of these interventions, but they did have methodological limitations, which should temper our conclusions. For instance, some studies measured meat consumption based on what people remember having eaten. That can create what’s called social desirability bias: If someone wants to behave differently, they may report something that is different than what they actually did. That is, maybe you’re changing people’s minds about what they want to eat but not their behavior. In future work, we want to collect actual measures of what people are eating, such as purchase records from college dining halls or café receipts.

The studies we examined also had short follow-up times. Most studies measured participants’ intentions or behaviors almost immediately after the intervention, which means we don’t know how long the effects last.

I think what we’ve learned so far is quite encouraging, and there is a lot of scope to keep building our knowledge.

About Stanford Medicine

Stanford Medicine is an integrated academic health system comprising the Stanford School of Medicine and adult and pediatric health care delivery systems. Together, they harness the full potential of biomedicine through collaborative research, education and clinical care for patients. For more information, please visit med.stanford.edu.

2024 ISSUE 1

Psychiatry’s new frontiers