Okay, now this is one I can def be of use in. KidsHealth has a section of the site called recipies for teens with cystic fibrosis found at :
About Recipes for Teens With Cystic Fibrosis
Since people with cyctic fibrosis suffer from malabsorption and very often have low appetite, all of these are very very high calorie (we're talking 1200 calorie single-serving chicken dishes)
Second, buy scandical (I suggest getting several containers at once) and use it religiously- scandical is an absolutely tasteless powder you can sprinkle into just about anything, and it adds 35 calories for each spoon. Pasta, soup, jam, drinks, whatever. If it's even slightly liquidy, it'll work. it can be purchased online at
Axcan Pharma Inc. :: SCANDICAL
Third, sip on high calorie drinks instead of cola or the like: your local store will probably have "ensure" or "boost" or "pediasure" type drinks which tend to be between 200/300 calories per serving, which is significantly more than most sugared drinks, and has a much much greater vitamin content.
Forth, and this goes with the above option, talk to your doctor about medical foods with more caloric density than can be found in drug store brands. Surprisingly enough, if your insurance wont dole out for it, Ebay can be a great place to find medical foods- at any given time, there's at least 30 people selling extra sealed tins of Elecare because their child outgrew their allergies, or whatnot.