The Easter (Great Lent) fast lasts 48 days and is both the longest and strictest fast in the Orthodox tradition. According to the calendar, on weekdays people fast with food prepared "on water" (means - no added oil), while on weekends oil is allowed and wine as well. Fish is only eaten on certain holidays: Palm Sunday and the Annunciation. The basic rules are to avoid all dairy, meat and eggs.
How strictly someone fasts can vary depending on their work, physical demands, health and personal ability. In past years, I followed the rules almost exactly like monks in monasteries, but this year I feel I need more omega-3, so I eat sardines and use olive oil more often.

Overall, it isn't extreme, it's a matter of good will and faith. It's also about focusing on prayer, doing good deeds and avoiding bad thoughts, actions and vices. Many people try to quit or reduce smoking and drinking during this time. There's a saying that captures the essence of fasting: it's so that "we don't eat each other". 🥰