Adrienne, if she is breastfeeding, maybe she is not keeping him at one breast long enough? Swip-swapping from side to side and not allowing the baby to feed from one until it feels empty means the baby doesn't receive the hindmilk which is where the fat is.

I can imagine how difficult it is to give advice as a grandparent/mother. Often we get told we are old fuddies and times have changed..breast technology hasn't!