Mine fasts every winter, from late September/early October until the first part of May. Last winter he was new to me and underweight already. He lost an additional half pound (sorry, no gram scale here) before he started eating, but then I put 1.5lb back on him before he quit again. This time, he lost 0.2lb the entire time. Now he has eaten two weeks in a row and has been looking for his next meal the last 2 days (one more day to go before feeding night).