I am a cradle Roman Catholic covert to Eastern Orthodoxy (oca). My understanding of the suggested rule for fasting during Great Lent is as follows: The week before lent no meat (beef, chicken, fish) all else is allowed.
Monday of the first week Clean Monday no food or drink except water. Tuesday no food or drink except water. Wed. no food or drink until after pre-scanctified liturgy, then only raw fruit or veggies. Thurs. and Fri. the same. Then the regular fast begins. No meat, fish, dairy, olive oil or wine Mon- Friday. Weekends oils and wine is ok. Fish is allowed on the Feast of the Annunciation and Palm Sunday as are oil and wine. Fish with no backbone is always allowed during regular fasting. Clams, mussels, scallops and squid along with shrimp and lobster. In most circles wine also means beer and hard liquior. In some olive oil also means all oils. Fasting is done in conjuction with an increase in your prayer rule and attending services and almsgiving. One done without the others is done in vain. Children, the elderly and the infirmed are exempt from the fast and with a blessing from your priest or spiritual father you can tweek the fast to suit your situation be it for health, family or some other reason. Most are warned not to āread food labelsā or to tell people you are fasting and refuse to eat what is served to you in hospitality,. since food has little to do with the spirit of the Great Fast. Hope this helps.