It is my understanding that as long as you avoid overly fatty rats like jumbos and you feed them just enough to keep them from getting overweight they will be fine.
Fatty liver comes from power feeding as youngsters in order to get them to breeding size faster.
Ours womas have been on rats since we have gotten them but we feed meals just big enough to show a slight bulge. When they were on hoppers we fed them about every 5 days now that they are a bit older (about 18 months) they get a small rat every 7 days. This has yielded a steady growth rate but they all maintain the nice shape with a defined dorsal line and by no means are overweight. The only difficulty in this is they are always hungry and handling without getting bitten was fun. They have just recently began to mellow out and have become quite pleasant to handle. They are super active and come out to you when you open the enclosure door.
On a side note, one our females (the most voracious feeder) appears to have a throwback from what appears to be the larger woma local. Her pattern is just like her siblings however her head is identical to the nearly patternless one in the pdf you posted. The head is elongated and the eyes are much smaller in relation to the head than the other two.