Veggie Challenge: Involving Family And Friends Helps

Reducing how many animal products we eat — like meat, dairy, and eggs — is one of the most powerful things individuals can do to help the planet, improve their health, and prevent animal suffering. Yet, even people who are motivated to change their diet often struggle to stick with it over time. One emerging solution is mobile apps and digital challenges that offer tips, motivation, and meal ideas for cutting back on animal products. But do these tools actually help people follow through?

This study set out to test whether a 30-day app-based challenge could help people reduce their animal product consumption, and whether the effect would last longer if people did the challenge with friends or family.

To do this, the researchers ran a randomized controlled trial with 1,213 adults in the Netherlands and Flanders (Belgium), all of whom had signed up for the Veggie Challenge on the ProVeg platform and wanted to eat fewer animal products. Participants were randomly assigned to one of three groups. The control group only filled out surveys sent by the researchers. One treatment group did the 30-day Veggie Challenge individually using an app that provided recipes, habit tracking, and environmental feedback (like how much water or emissions and how many animals they saved). The other treatment group did the same challenge but was encouraged to invite a friend or family member to join them. This “social challenge” group also got access to features that allowed for team-building and shared progress.

Participants reported how often they consumed animal products during a three-day period at four different timepoints: before the challenge, right after it ended, and again one and three months later. The outcome variable was the total frequency of animal product consumption across those three days. The maximum possible score was 96 — representing all eight animal product categories (chicken, beef, pork, other meat, fish or seafood, cheese, other dairy, and eggs) consumed at every meal over 12 meals (breakfast, lunch, dinner, and snacks). The researchers looked at how the groups differed in their average consumption at the end of the challenge and one and three months post-challenge.

At the end of the challenge, both intervention groups had reduced their animal product intake by about 16 to 17% compared to the control group. However, only the social challenge group maintained a statistically significant reduction in animal product consumption three months later — suggesting that bringing in social support helps make the change stick.

Looking closer at the types of animal products, the biggest reductions were seen in meat consumption. Both treatment groups cut meat intake by 22 to 27% right after the challenge, but only the social group kept that reduction at the three-month follow-up (25% less than the control group). For dairy and eggs, there were short-term reductions (11 to 15%) that didn’t last beyond the challenge.

The challenge seemed to work best for people who were still eating meat at the beginning of the study. Those who had already cut out meat saw less of a change. Interestingly, participants who chose more flexible goals — like having “meatless days” — reduced their animal product intake more than those who aimed to go fully vegetarian or vegan, suggesting that more flexible, less demanding goals might be the secret to success.

There were also some limitations. While the app was available to all participants in the intervention groups, only about 65 to 70% actually reported taking part in the challenge. That means the results reflect the effect of being encouraged to participate, not necessarily what would happen with full engagement. In fact, the true effect might be stronger among people who actually engage with the challenge as intended.

In the social challenge group, only about 12% of participants used the app to formally invite someone, so the benefits of social support might even be underestimated. Still, the encouragement alone — whether or not it led to formal team-building — seemed to help people stick with their new habits longer.

It’s also worth noting that the study focused on people who were already motivated to change their diets, most of whom were women and highly educated. That means the results might not apply to the general population, especially people who haven’t yet considered reducing their intake of animal products. Moreover, participants were already relatively low consumers of animal products at baseline, averaging just above 8 servings over three days (out of a possible 96 servings). This suggests the sample may not reflect higher animal product consumers, and the room for dietary reduction was somewhat limited.

Overall, the study suggests that app-based diet challenges can be a useful, low-cost tool to help people reduce their consumption of animal products — especially when they include a social element. For advocates, this means designing plant-based campaigns that encourage people to involve friends or family and set achievable goals, like cutting out meat a few days a week. When dietary change is framed as a shared, flexible journey rather than a strict solo effort, it becomes easier and more likely to last. These effects may be especially strong for people who regularly eat meat and are already motivated to cut back.