I am Catholic, but I don't follow that whole "No meat on Friday" ish. Never understood what purpose it served.
Then, I had a friend (who in school, studied religions) who told me that back in the day, the fishing industry was having severe financial issues.
To help, the "church" created this law about not eating meat on Fridays. That way, the fishing industry was ensured that at least one day, people would be buying fish, and stimulate the industry.