Beswitched
That was my understanding too. I've never heard of Shrove Tuesday being a day of Fast and Abstinence.
That can't be right. The Germans in (very Catholic) Cologne call the season (culminating in a wild Extended weekend from the Thursday leading up to Shrove Tuesday) ... well, they call it Carneval. The Carne part refers to meat. So you would indulge in meat and rich foods and drink. This would fit in with the yearly cycle in the Northern hemisphere when stores could be plundered as soon fresh produce would be available with the approach of Spring and young animals are born.
From Ash Wednesday on, i.e. during Lent, is when you're supposed to fast, not eat meat etc. I can't imagine that the tradition is much different in Protestant churches because it is based on the 40 days that Jesus (and, I think, before him, his cousin John) spent fasting and doing penance in the desert.