I have three RIR hens that are turned 2 in early June. In late July, they had a true, full moult, and looked really funny, all bare all over of major feathers and covered in porcupine quills. I felt sorry for them, they looked itchy. Anyway, they of course quit laying at that time, and today, I heard the egg song again for the first time. I also, coincidentally, moved them to a different run during their moult, in order to do some repairs and maintenance on their original coop and run. So, today, I said, "it's time to go back to the first coop, girls" Well, when I picked each of them up, I couldn't believe how FAT they are -- like the scene in Chicken Run when Mrs. Tweedy measures the one hen and says "Double their rations, I want them all as fat as this one!" I guess egg laying really does take a toll on their bodies, and being off of it for a while let them fatten up. They have constant access to Purina Layena pellets, and I also give them tons of fresh produce and household scraps, so it's not like they are ever underfed, they can eat all they want. It was just interesting to me that they would gain so much weight. While I obviously don't have quantitative data, I'd say their body mass has increased by something like 50-60%.