I slipped up on my vegan diet. Now what?

The objection

“I went vegan, then caved and ate a cheese toastie. So I’ve blown it, I might as well go back to normal.”

The answer

The objection scores veganism like a purity test, where one lapse turns you from innocent to guilty and leaves nothing worth protecting. What veganism changes, how many animals are bred and killed to feed you, works more like a running total. Nobody who eats meat every day thinks a salad has spoilt their record, and one toastie hasn’t spoilt yours.

Does one slip undo the good you’ve done?

One slip doesn’t undo it, because what a plant-based diet spares adds up meal by meal and a slipped meal takes back only its own share. In 2021 Animal Charity Evaluators, an animal charity research group, divided the number of vertebrates killed for food worldwide by the number of people who aren’t plant-based, using 2018 figures for land animals and 2017 figures for fish, and arrived at about 105 a person each year, 93 of them fish [1][2]. It calls the result “a very rough average”, and it doesn’t allow for how closely farms cut output when people stop buying [1]. However closely farms follow demand, the same discount applies to one slipped meal as to a whole vegan year, so going back to normal gives up every plant-based meal to come because of one that went wrong.

Why does one slip make people want to give up?

Research on relapse, mostly among drinkers, suggests guilt can turn a lapse into giving up: people who read a lapse as proof of a personal failing, such as “I have no willpower”, are more likely to abandon the attempt than those who put it down to a situation they weren’t ready for [3]. Relapse researchers call this the abstinence violation effect, and Larimer and colleagues’ 1999 review, written for alcohol treatment, says a lapse greatly raises the risk of a full relapse but doesn’t make one inevitable [3]. Relapse-prevention therapy teaches people to treat a lapse as a mistake that shows where more planning is needed, and to look at what set it off [3]. For a new vegan that might be hunger, a family meal or a long day with nothing in the fridge, and each of those can be planned for.

Giving up is common, and it tends to come early. In a 2014 US survey of people aged 17 and over by Faunalytics, an animal-advocacy research group, 84% of those who had ever been vegetarian or vegan had given it up; a third of them had lasted three months or less, and just over half less than a year [4]. More than a third of those who had stopped said they would like to try again [4].

What if you ate something by accident?

An accident doesn’t make you any less vegan, since the Vegan Society defines veganism as seeking to exclude the exploitation of animals “as far as is possible and practicable” [5]. UK food law makes businesses declare 14 allergens, among them milk, eggs, fish, crustaceans and molluscs: on packaged food they must stand out in the ingredients list, for example in bold, and restaurants, cafés and takeaways must give you allergen information, according to the Food Standards Agency (2026) and, for Scotland, Food Standards Scotland [6][7]. Meat itself isn’t one of the 14, and nor are meat stock, animal fats such as lard, gelatine or honey, so none of them has to be picked out in bold and the whole ingredients list needs reading; the page on hidden animal ingredients covers the less obvious ones. A product labelled vegan saves the reading, because the Food Standards Agency says the label means no ingredients of animal origin were intentionally used [6]. Note whatever caught you out and look for it next time.

Will one slip set the new habit back?

One slip is unlikely to set a new habit back: when 96 volunteers each took up a daily eating, drinking or exercise routine in a 2010 study, missing a single opportunity made no material difference to how the habit formed (Lally and colleagues) [10]. The habit itself takes months to form, though. A 2024 review of 20 studies of new health habits found four that timed it, two reporting medians of 59 and 66 days and two reporting averages of 91 to 154 days, and concluded that health habits typically take 2 to 5 months (Singh and colleagues) [9]. In the study that looked only at healthy eating, individuals took anything from 4 to 335 days, and only 23% reached the researchers’ threshold for a habit at all [9].

Cravings tend to loosen too. A 2018 review, drawing mostly on weight-loss research, found that cravings for particular foods fell as people ate those foods less often (Myers and colleagues) [8], so if it was a craving for meat or for cheese that won this time, it should lose its grip the longer you go without.