I would agree that 10g is a whole lot for only 6 weeks of fasting. One of my girls stopped eating for 5 weeks this winter and lost less than a gram in that time (from 56.6 to 55.7). I would be worried something else is going on.
+1 to the doc. I should get a scale and weigh my leo, but she has rarely been eating for about 3 weeks now. She doesn't look any thinner at all. Tail is still REALLY fat and all that.