That is very true, I had ones with alot of fat while this last batch had very little. The last batch I pastured and restricted their feed and this kept the fat down. However on earlier batches I gave them much more and the produced more fat as a result. As far as actual weights go I would say six ounces for unrestricted and maybe two for pastured, but that is a rough guess.
Is there a particular reason for the question.
I fed mine meat crumbles and they had very little free-range and there was very little fat on them. 31/2 - 41/2 lb. birds. I was surprised as this was my first time doing this.
I'm not sure how to measure that, but adding corn will increase the fat. Either way, they will be fattier than the store bought birds you normally see.