To meat, or not to meat: A longitudinal investigation of transitioning to and from plant-based diets.

Concerns over potential negative effects of excessive meat consumption on both the environment and personal health, coupled with long-standing debates over animal rights, have motivated research on the prevalence and predictors of plant-based versus meat-based diets. Yet few studies have examined longitudinal trends in dietary behaviours using large national samples. We address this gap by examining the prevalence, predictors, and annual change in the self-reported dietary behaviour of a large national probability sample of New Zealand adults (categorised as omnivore, vegetarian, or vegan; Ns = 12,259-50,964). Consistent with our pre-registered hypotheses, omnivore was the most prevalent dietary category (94.1%). Moreover, higher levels of conservative ideologies (i.e., political conservatism, Right-Wing Authoritarianism, and Social Dominance Orientation), lower subjective health, lower environmental efficacy, and lower disgust sensitivity predicted having an omnivore (vs. vegetarian or vegan) diet. Longitudinal analyses further revealed that the probability of shifting from an omnivore diet to a vegetarian or vegan diet over a one-year period was low, and that veganism was the least stable dietary category. Both gender (men) and political conservatism predicted lower probabilities of transitioning from meat to no-meat diets over time.