One of my big girls I have now is a rescue I got in 06. She was 3 or so years old back then and less than 800g(two mice once a month). From May 06 to December 06, she gained over 1500g on a proper diet(2-4 mice a week) and in a proper environment. She's now gravid for the second year in a row(7 eggs!) and is around 2400g.