>>98920860Aside from the anon joking earlier, if you haven't had meat in a long while, eat even what to you may seem a moderate amount may cause indigestion etc, due to your body not being prepared to process meat (lacking specific enzymes/gut bacteria).
For example, from personal experience, for the people that practice Lent, you're not supposed to eat meat, fish, poultry, eggs, dairy, or olive oil, essentially being vegan for 6-7 weeks. When Easter comes, it is tradition to have your first meal be soup with chicken stock and eggs, and some chicken, to ease your stomach into eating meat again, then the next day you can eat meat barbecue at family celebrations. This tradition was likely born from the rudimentary understanding of how biology works in ye olden days, and so it continues to this day.
In a similar fashion, I imagine someone who has been a vegan for multiple years would require an even bigger acclimatisation period before starting to eat meat again. Also, keep in mind, lactose tolerance falls the less you consume dairy, so if a vegan goes years without dairy, it's quite common they'll develop lactose intolerance, often permanently.
