Wrenn finds that many organizations behind social movements loosen the expectations they have of their followers, allowing people to identify with the cause without actually changing their behavior. But this relaxed approach, she argues, jeopardizes the movement as a whole.

Take “flexitarians,” people who are interested in vegetarianism but still eat meat. Under Wrenn’s critical eye, flexitarians are an example of what she calls “free riders”: passive participants of a social movement who benefit from the work core members put into the cause. While permitting free-rider participation in a movement may extend its longevity, she contends, it ultimately weakens it by diluting a social movement’s message and making it more difficult for a movement to mobilize resources. An influx of free riders, Wrenn says, “maintain[s] the illusion of mass support, [while] real power is reserved for core members.”

Beyond ‘vegetarian’

“Those eating flexitarian aren’t really eating any less animal products,” Wrenn says. “Other research finds that participants asked to eat prescribed diets of omnivorism, flexitarianism, and veganism experienced similar levels of satisfaction and adherence to the diet. So why not go for the gold and ask folks to go vegan?”

Wrenn points to 25 studies she says showcase the shortcomings of allowing flexitarianism or an unstructured “incremental” conversion to veganism. A 2012 study of Canadian vegetarians and ex-vegetarians found that flexitarians who quit eating meat because of health or environmental reasons were more likely to relapse to meat eating. A 1993 British study found that only a quarter of people who considered themselves to be reducing meat intake actually did.

For an example of successfully encouraging consumers to give up something they love, Wrenn says, look to smoking-cessation campaigns. One 2007 study found that smokers are more likely to quit when they’re either asked to stop smoking immediately or put on a specific, scheduled smoking-reduction plan, as opposed to simply being asked to “cut back.” (The percentage of adults in the United States who smoke declined from 20.9 percent in 2005 to 15.5 percent in 2016.)

Despite Wrenn’s findings, history has shown that in some cases, slower, more incremental change has benefitted the vegan movement. Elizabeth Cherry, the author of Culture and Activism: Animal Rights in France and the United States, notes that a more practical, gradual approach worked for the American vegan movement, beginning in the ’90s. “I found that the U.S. [vegan movement] used a cultural logic of pragmatism, meaning they just used whatever worked, regardless of whatever they may personally think about it,” such as appealing to people’s concerns about health, she says. The French vegan movement, meanwhile, “chose from their tools using a cultural logic of consistency, meaning that they only used the tools that exactly aligned with their beliefs.”