One thing to keep in mind: when adding large amounts of fat to foods, keep a close eye on stools over the next day or two. Sometimes they will tolerate certain fats better than others so maybe try adding a certain type of fat one at a time, watching stools & adjusting enzymes if needed, etc before adding a new one. It won't help to add tons of calories if they are losing it all the next day in greasy stools. For example, Emily cannot tolerate large amounts of heavy cream, even though she LOVES it and it would be a great way to get a lot of calories into her on a daily basis in the form of whipped cream (on fruit, w/ dessert, as well as in food.) Even twice as many enzymes as she'd have with dinner don't help with the gas and greasy stools she has the next day if she has frequent doses of heavy cream. But she tolerates other forms of 'straight' fat in her diet much better.
Whipping cream or heavy cream is the highest fat stuff you can get, I think, when it comes to milk products. Heavy cream comes in at 50cal per tb and at least 36% milkfat. Table cream varies somewhat... it's higher fat than 1/2&1/2 but lower in fat than whipping cream or heavy cream (which are almost the same when comparing the box... light cream is less, as implied by the label.) Emily can tolerate some 1/2 & 1/2 in her food much better than cream, and does ok with Scandishakes (which are very high-fat) ...but Scandishakes are also MCT fat, more easily digested by those with CF, a trade-off for the fact that they are high in sat. fat.
Sometimes what they like will end up being a fat some people will insist is a 'horrible' fat for them to have... we have to have some leeway there. Our kids face so many obstacles and growth failure is a nasty one too. I go for the good fats when I can but if she loves bacon and sausage and can get a bit of protein along with a bazillion calories while she's scarfing it down, I have to push some of my worries about sat. fat to the back of my mind in the process. I do, however, make a point of avoiding margarine & shortening with trans fat and picking margarine and oils high in Omega's.
Nuts: great suggestion. Not only high in fat, but most are high in the good type of fat as well as containing protein and fiber. Emily has recently discovered pistachios and I nearly swoon watching her scarf down an enormous pile of them... salted, even better... (and fine-tuning her very-delayed fine motor skills shelling them, a great bonus too.) <img src="i/expressions/face-icon-small-happy.gif" border="0"> Just make sure they have enough enzymes with nuts- they can easily consume the fat and calories of a whole meal with a relatively small quantity of them.
Emily loves fast food but even with the temptation of the massive calorie load I don't do it more than occasionally... because if she has it all the time so would her brothers ($$$)...
I am finding it's a challenge getting enough fruits and veggies into her with her needed calorie load and I hate making that sacrifice. I don't agree with it at all: our kids have enough trouble with their nutrient absorption and not getting these foods from their natural sources is not going to help (a vitamin is just not good enough, it's supposed to fill in the gaps, not be a substitute for a diet aimed at filling nutritional needs.) And adults that enjoy fruits & veggies are generally people who grew up eating enough of them... she loves them now and I don't want to blow that, you know? So I am struggling with that one at this point.