Tactics In Practice: The Science Of Vegan Challenges

Author: Björn Ólafsson | Published: June 11, 2025

Estimated Reading Time: 23 minutes

Vegan challenges have become a popular way to encourage dietary change. This deep dive gets into the nitty gritty of what makes a challenge achievable.

This is the fourth edition of Faunalytics’ Tactics In Practice (TM), a series of resources where we explore the science behind different animal advocacy tactics and how you can make the most of them for animals.

In this edition, we’re taking a deep dive into challenges and pledges, including Meatless Mondays and Veganuary.

How Do Challenges Work?

Challenges, commitments, and pledges are essentially the same intervention: the commitment of individuals to a goal that helps them reduce or eliminate animal consumption for a specific time period. Challenges can vary wildly, and sometimes have other goals: creating larger cultural change around veganism, promoting vegan brands, and influencing the media. Many involve messaging campaigns, mentorship, support groups, and can be implemented on an individual level or an organizational level. Two challenges that have become relatively household names — Meatless Mondays and Veganuary — are notable for being both an individual pledge and focused on institutional reform. We’ll explore both in greater depth later.

Note: “Challenges,” “pledges,” and “commitments” aren’t defined terms in the research literature, to the best of our knowledge. Some (but not all) advocates we spoke to use the word “challenge” to indicate a more-involved form of a “pledge,” perhaps one with support groups and resources, whereas a pledge is more individualized. However, because these terms are neither centralized nor strictly defined, we will use them interchangeably in this resource.

The simplicity of pledges may be the key to their success, according to many advocates we spoke to — by lowering the barriers of entry for diet change, more individuals are likely to take part. Psychologically, we were able to identify how challenges affect us in a few key ways:

In regards to vegan challenges in particular, a month-long abstention from meat could potentially foster “meat disgust,” which is a good predictor of reduced meat consumption. The materials provided by challenge organizers — like vegan recipes, community organizing, videos of animal intelligence or suffering, and information about the agriculture-climate connection — also help address some of the biggest barriers to veganism, such as feeling unhealthy on the vegan diet, low identification with veganism, believing society perceives veganism negatively, low autonomy support, and more.

Just as important as the how is the who: those who end up participating in a challenge or pledge are usually already somewhat internally motivated to create personal change. Some data backs this up — in one undergraduate thesis, when students were assigned to Meatless Mondays, they weren’t able to reduce their meat consumption at all. In other words, it’s likely that the average challenge participant has more motivation than a regular meat-eater, and that’s okay! We can view ideal challenge participants as those already somewhat open to veganism (for example, those contemplating or planning a vegan diet transition). Another randomized controlled trial found that, of people who were somewhat open to diet change, those who were asked to sign up for a vegan challenge were more likely to go vegan than a control group. Basically, while vegan challenges target people who are already somewhat open to veganism, the challenge itself speeds up or triggers the diet transition process.

How Effective Are Challenges And Pledges?

A comprehensive 2013 meta-analysis of climate-oriented commitments showed that the pledges were able to create behavioral change, both during the intervention period and even after the pledge was over, although the effect wasn’t as strong after the pledge ended. In our research, we couldn’t find a similar meta-analysis for plant-based pledges, so instead we reviewed the internal data of a few vegan challenge organizations.

We found multiple surveys, comprising nearly 10,000 total individuals across the world: our analysis of Challenge 22, post-Veganuary public surveys (we used 2024’s), Vegan Outreach’s 10 Weeks to Vegan, and Animal Outlook’s VegPledge. We also reviewed some internal, unpublished data that we can’t share links to: a survey from YouGov of Veganuary participants, data from Desafío 22 (an offshoot of Challenge 22), and a survey from Dyrenes Alliance.

We found that the average conversion rate (defined as a meat-eater becoming a vegetarian or vegan after the challenge ends) ranged between 10 and 28%.

This is a rather optimistic range! At the bottom of this resource, we’ve included research-backed tips we think may be able to improve these numbers even more.

Most organizations also found that, on average, challenge participants still reduced their meat consumption even if they didn’t stay vegan after the challenge ended (e.g., this study in Denmark or Veganuary’s six-month follow-up surveys). This checks out — our research into vegan retention found that former vegans tend to eat less meat than they did before trying veganism.

Finally, in our landmark 2022 study that measured the impact of different interventions on diet change, meat-free challenges in general were found to be very effective. They were the second most likely intervention out of sixteen to have reduced participants’ meat consumption, trailing only books. Overall, we estimated that 14% of the entire U.S. population had reduced their meat consumption due to meat-free challenges.

Meatless Mondays

Sometimes called “Meat-Free Mondays,” this intervention seeks to eliminate meat consumption on its titular day of the week. Similar to Veganuary, it can function either individually (a personal pledge or resolution) or collectively (a workplace or university challenge). Meatless Mondays (MMs) have been around for decades and, according to survey data, peaked in popularity in 2011. Still, Meatless Mondays is a household name — one that has expanded to 41 countries — and a well-known form of reductionist dietary challenge. While we were unable to find quality data that examines how many people worldwide have reduced meat consumption as a result of Meatless Mondays, we were able to understand other key aspects.

An advantage of the Meatless Monday approach is that a reductionist message may appeal to some people more than an elimination message would. For example, our research has found that asking people to reduce meat consumption leads to fewer meat purchases than asking them to eliminate their meat consumption. Therefore, while MM campaigns are sometimes criticized for watering down a vegan message, the approach can be quite beneficial for long-term meat reduction.

One of the most critical questions in assessing Meatless Mondays’ impact is whether Meatless Mondays can convince people to eat less meat throughout the week. In research terms, we call this behavioral spillover: are there any ripple effects from choosing to not eat meat one day a week? Existing research suggests that the answer is yes.

In one survey of Meatless Monday newsletter subscribers, people actively abstaining from meat on Monday were 15 times more likely than people who ate meat throughout the week to reduce meat consumption on other, non-pledge days. They were also five times more likely to cook meatless at home and three times more likely to order meatless in restaurants. The longer they had been receiving the newsletter, the more likely they were to be reducing meat consumption. Secondly, a survey from Meatless Mondays suggests that, of people who have been influenced by the MM campaign, 26% have incorporated more meatless meals throughout the week and 20% eat more meat-free meals when dining out. Finally, a survey of MM participants in Massachusetts found that 31% had gone on to further meat reduction after taking the pledge.

Real-world trials also offer insights. In a series of 2018 surveys tracking the impact of Meatless Mondays at New York hospitals, 41% of staff were trying to cut back on meat before the initiative, as compared to 45% the following year at the tail end of the program — and 53% of total participants cited Meatless Mondays as a reason why. In one study of people who signed up to the Meatless Monday official website, 30% of participants who had been doing MM for five or more years no longer ate meat at all: they were more likely than other participants to have engaged in more features of the website and have seen more benefits to a vegetarian diet. All in all, while this data is correlational and survey-based, it does indicate that participation in meat-reduction pledges like Meatless Mondays are likely to predict, and possibly spark, future meat reduction.

However, institutional versions of meat-free days are unlikely to create long-term meat reduction, according to a recent study. The analysis, which covered meat-free days across 18 months in a university campus, found that the day after a meat-free day had 3.5% more meat purchases than normal. This means that if advocates are instituting meat-free days in food service settings, they will likely need to pair this intervention with other tactics, like educational campaigns, posters, lectures, or something similar, if they want the meat reduction to last.

When it comes to Meatless Mondays, our research has identified which groups are most open to instituting one: liberal people, women and non-binary individuals, folks concerned about climate change, and those with graduate degrees are most likely to support such an initiative.

Meatless Monday campaigns (wherein an institution will promote MM or possibly remove meat from the menus on Mondays) usually have positive acceptance rates among participants, although it’s not universal. In one survey of cafeteria staff in New Zealand, 59% of participants held a positive opinion of Meatless Mondays, compared to 10% neutral and 31% negative. Those who held negative attitudes explained they felt that removing choice on menus was unethical, that the food was subpar, or that there were better ways for the institutions to be more sustainable. Qualitative data from MM programs (one in Norway and another in the U.S.) also found some level of pushback and lack of conviction for these programs, with some people saying they felt “forced” to change.

Importantly, successful MM institutional campaigns should involve listening to participant feedback and getting buy-in from both staff and consumers. When this occurs, Meatless Mondays also appear to engender some institutional shifts in food consumption — one 2012 survey found that 49% of venues with Meatless Mondays saw an increase of plant-based orders, while 30% saw a decrease of meat orders.

If you are considering an MM initiative, we strongly recommend reading this resource in particular, especially the recommendations section on pages 35–40, as well as Meatless Mondays’ resources page. Alternatively, read our review of plant-based defaults, which are similar to institutional MM campaigns but rarely received pushback.

Veganuary

“Veganuary” is both a challenge and an organization. They work with individuals through their titular “Veganuary” 31-day vegan challenge, as well as with corporations and the media. For the purposes of this resource, we’re going to primarily focus on Veganuary as a challenge, not conduct an impact analysis of the organization as a whole.

Based on representative survey data, an estimated 25.8 million people took part in Veganuary in 2025. This includes people who “officially” took part via the website and newsletter and those who partake “unofficially” — like a personal New Year’s resolution. Using official sign-ups as a benchmark, we can see that Veganuary is growing annually.

The cultural impact of Veganuary is hard to overstate, especially in the United Kingdom. According to U.K. survey data, 23% of current vegans and 20% of U.K. vegetarians have taken part in Veganuary, while a YouGov survey shows that an estimated 9% of the entire U.K. population has taken part.

Similar to Meatless Mondays, a potential big advantage of Veganuary is the behavioral spillover: are participants more likely to eat vegan after taking the challenge? Existing research suggests that the answer is yes. Survey data from Veganuary 2024 shows that 27% of official participants remained vegan, while a further 54% reduced their meat consumption by half or more. Unpublished, representative survey data we reviewed from YouGov pegs those numbers at 23% and 43%, respectively. Meat reduction is reflected in supermarket data as well, although to a lesser extent: over six months, Veganuary participants reduced meat consumption by 5.4 kg (11.9 pounds) per person on average — or about an 11% reduction in total consumption.

The movement appears to be quite popular, and a series of studies show that the online reaction to Veganuary is largely positive. One study found that 62% of tweets about Veganuary were positive and that many of the negative tweets had negative sentiments towards animal cruelty, not the challenge itself. Our own research found similar results: 64% positive sentiment, compared to 23.5% neutral and 13% negative. In fact, use of the word “vegan” spiked in January in general, likely due to Veganuary and general New Year’s resolutions. However, another social media analysis found that most brand content and most activist content reached entirely different audiences, suggesting that ethical arguments may have remained siloed.

One key goal of Veganuary is to change our food service venues to make vegan food more accessible. In this area, Veganuary seems to be successful. In a study from Cambridge that analyzed nearly five million meals sold over six years in 131 workplace cafeterias in the U.K., researchers found huge boosts (86–113%) in vegan meal sales as a proportion of the total during three Veganuary campaigns. A similar 2022 study found a 57% plant-based product boost during January, one that remained 15% higher than baseline after the month ended. However, the authors found no evidence of reduced meat sales (although they noted that the study took place during a COVID-19 lockdown, so it’s possible that consumers were buying more food than normal, which skewed the results of meat purchases). German food consumption data also showed that sales of meat in Germany were nearly 30% lower in January compared to December 2024. In other words, real-world data shows that it’s likely that Veganuary can promote plant-based foods effectively.

How To Make Better Challenges

Target Communities, Not People

One theme that has emerged in the animal protection movement in the last few years is that working with individuals on diet change isn’t as effective as working with groups. The logic is sound and backed up by research: since social ties help retain vegans, working with groups of people is more likely to make diet change stick. Check out our study on the social spread of veganism or another study on social support’s impact on plant-based diets for some examples of this key point.

Given this existing data, we weren’t surprised to see a 2021 study that found that some of the biggest barriers to Meatless Mondays were family and friends not enjoying the meatless dishes. The study also had a bit of optimism: 59% of those who discussed their pledge with their loved ones reported that it led their family members to commit to meat reduction as well. Another 2024 study found that while both an individual and social challenge app were able to reduce meat consumption during the challenge, after the challenge ended, only those who used the app in a social context kept up their plant-based habits.

This is an important lesson for challenge campaigners: work with communities, not just people to create lasting diet change. Of course, that’s easier said than done, especially when many challenges are virtual. Some campaigners have suggested holding Zoom meet-ups to encourage community, targeting existing communities with online marketing (such as nearby university students or members of a specific sub-group like Black U.S. Americans or people who keep kosher), or forging partnerships with in-person communities like churches, fitness centers, hospitals, or neighborhood groups.

Regardless of how you go about it, remember that diet change is hard — social bonds can make it easier.

Make Your Pledges Active, Public, Flexible, Specific, Forward-Looking, and Forgiving

Not all challenges are created equal! If you are designing a pledge, follow our guide here — make them active, public, flexible, specific, forward-looking, and forgiving.

Get Buy-In From Staff

If your pledge involves some form of institutional or corporate outreach (like a university or workplace challenge), make sure that the staff understand the point of the campaign. Multiple studies show that staff not understanding the point of these campaigns and challenges can be a factor in their failure. In particular, when staff themselves are able to contribute to the menu, they are more likely to support a Meatless Mondays program, according to a U.S. qualitative study.

If removing all meat items from a menu is unpopular enough to cause backlash (which was noted in a few studies), consider implementing a plant-based default instead, which typically has a 90%+ approval rating. Check out the earlier edition of the TIPs series for an overview.

Pair Pledges With Other Interventions

Given the theory of how pledges work, it may not be as strategic to use them in isolation, but rather as one tool to trigger further pro-animal actions. For example, ask participants to make a vegan pledge after watching a slaughterhouse documentary or, during the pledge, try to encourage participants to donate to a farmed animal protection organization.

There’s evidence this works. For example, one study in a university found that 39% of students who studied meat ethics and were then asked to do a 24-hour vegan pledge took it and then actually followed it. While one day is an amount of time far smaller than most pledges, the study shows that pairing challenges with other forms of advocacy, like education, can be a worthwhile strategy. Similarly, a cafeteria nudge study found that combining a meat-reduction pledge with nudges worked better than the nudges alone.

Vegan challenge advocates should think critically about how their intervention fits in with the larger diet change movement. Are there avenues for collaboration with other groups? What is the ideal “next step” after a challenge? Are there other interventions that can support the effectiveness of vegan challenges or vice versa? Reflecting on these questions is likely to result in bigger impact.

Focus On Removing Barriers To Veganism

People need to know how to eat less meat — something often reflected in the reports of vegan challenges. In a study of the social media presence of the users of a month-long vegan challenge in Finland, participants discussed the functional practices (like cooking and buying), ethical and sustainability impacts of animal farming, and the formation of a vegan “identity” as potential barriers. This tracks with some of the barriers experienced by those doing meat-free challenges, such as one study that found lack of support from others, feeling that it was inconvenient or that they did not have the time, and trying to avoid food waste by eating leftover animal products as obstacles.

Some research suggests that pledges only work with support systems in place. In one 2022 study, German, U.K., and Australian meat-eaters were told to pledge to do their best to not eat meat for 28 days. People who were initially more motivated in the challenge and believed themselves to be capable of fulfilling it were more successful. Interestingly, people who were told to pledge to reduce meat consumption had greater meat cravings during the pledge period. While their meat consumption went down for that month, it bounced back to normal after the four weeks were up — however, this challenge only involved a pledge without any form of parasocial or social support, which could have improved long-term outcomes.

Tailor Support To Different Demographics, And Target Influential Groups

In doing our research, one finding stuck out as curious — meat-free challenges were one of the interventions most likely to cause Black U.S. Americans to feel anger towards animal advocates. We’re not sure why, but it may be due in part to these challenges feeling “forced” onto communities that don’t feel represented in the challenges themselves. To us, this indicates that any meat-free challenge campaigner must be very mindful of how different demographic groups respond to dietary change.

Not everyone needs the same type of support when going vegan, so make sure your supplementary materials are tailored to different types of people. For example, Challenge 22 has a special program for parents, as parents are usually responsible for feeding entire families and can thus have a larger impact on societal meat reduction than other individuals.

Integrate Brand Awareness With Movement Goals

While it’s great that large-scale challenges like Veganuary and Meatless Monday are able to boost plant-based sales, research suggests there is untapped potential to merge the brand side of things with the activist side of things. In other words, it may be strategic for organizations to ride the wave of boosted sales from these challenges and promote pro-animal messages and general vegan norms more than they are already doing.

Vary Your Messages

It’s an old tune, but one worth repeating: no perfectly persuasive vegan message exists. Advocates need to be using a variety of messages based on the audience. Many studies (like this one on Meatless Mondays or this one on Veganuary) all show that participants in challenges have diverse motivations: health, climate, animals, social, etc. Remember that people reduce and eliminate animal products from their diets for various reasons, a fact your messaging should reflect.

Follow Up After The Challenge Ends

Since one goal of vegan challenges is to create long-term diet change, it’s worthwhile to follow up with previous pledgers to see what support systems they need or barriers they’ve run into. Activists we’ve talked to tell us that this is best done very gently — many people are wary of spam emails or overzealous campaigners. Still, it’s a mistake to think of past participants as fully “veganized.” Remember that vegan retention is a major issue our movement needs to work on.

Encourage Sign-ups For A Higher Success Rate

Veganuary’s “unofficial” (people going vegan in January without signing up) and “official” (people who signed up to the Veganuary website) data gives us some interesting insights. Notably, the success rate for registered participants is higher than the unregistered participants. This is likely due to many factors: more initial buy-in, more support systems, more public accountability, more resources, etc.

This should signal to challenge campaigners that it’s strategic to maximize the number of people who are “officially” committed to your challenge. Campaigners we spoke to mentioned that this often requires spending money on social media ads, which may be cost-prohibitive. However, unless you have reason to believe that unofficial pledgers are still succeeding at good rates, outreach for registration may be worth the price. You can also offer prizes for those who register officially, such as vegan cookbooks, donations to a charity of their choice, etc., to help boost official participation.

If you’d like more advice or need help finding insights to support your vegan challenges, we encourage you to contact the Faunalytics team or visit our Office Hours.

Faunalytics is deeply appreciative of the thoughtful contributions, insights, and resources shared by the following advocates: Marla Felcher (Good News Veg), Nathalia Dziadek (Dyrenes Alliance), Maite Chaves (Desafío 22), Toni Vernelli (Veganuary), Laura Radoi (Challenge 22), Doris Nemes (Challenge 22), Jenny Canham (Animal Protection Specialist), and Jack Norris (Vegan Outreach).

Sources / Read More

Meatless Mondays

Veganuary

Social Media Impact Of Veganuary

Other Challenges & Pledges

Supplemental Papers

Meet the Author: Björn Ólafsson

Björn Jóhann Ólafsson started advocating for animals at the ripe age of ten and hasn't stopped since. After studying psychology and human rights at the University of Chicago and the Center for Decision Research, Björn worked in education and science writing. He then investigated animal agriculture as a journalist for Sentient Media and other publications, reporting on greenwashing campaigns, alternative proteins, and animal sentience. Outside of work, Björn is often trail running in the Icelandic highlands or the Spanish Pyrenees, learning more languages, sewing outfits from scratch, or spending time with his two beloved lovebirds.

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