Babies and toddlers do need fat in their diet for growth and development, especially of the brain and nervous system. Definately don't worry about calories at this age, especially if he is losing weight - he needs it! SO ithink adding butter and cheese is a good idea - I would choose those over canola oil, because butter and cheese are good sources of vitamin A and D. As for saturated fat - some is needed for development as well. For instance, the fat in breastmilk is just under half saturated fat - and so is the fat in butter!