I think that if having a pig out day keeps you on plan the rest of the week then that is fine. I tend to go out for lunch on a Sunday and have a full main course [eg pork crackling, gravy, Yorkshire pudd etc] and occasionally a starter [prawn cocktail or melon if I'm really good]. I try to take care for the rest of the day. Obviously it would be better to stay on plan full time, but that is not realistic for a lot of people and as long as you don't give up altogether, I'd say i't ok. I know some will disagree.