If I could suggest a few things it would be to first work on inflammation. CF people have a tendency towards inflammation due to many factors (skewed fatty acid profile, tendency toward acidity, ect). When inflammation is constant in the gut, you can see issues like constipation (not enough movement in gut to move food through) or too much movement/spasasms causing nutrients to pass through too quickly. In addition, the lining or barrier in the gut can be too thin or non-existent setting up an environment for yeast overgrowth or a "leaky gut" type of situation. Often if one major system (such as the digestive tract) becomes chronically inflammed, other systems will follow especially the lungs and sinuses as they are connected.
We feel by helping our son keep inflammation at bay, he absorbs nutrients better and has less lung issues. I feel it is something that is not addressed in traditional approaches and that until it is under control, you can give all the calories you wish but the gut just isn't equipped to handle them or utilize the nutrients properly. I am not an expert on mutations or their role, but I can share what we have done and discovered along the way.
Here is what we do:
Probiotic: Since before diagnosis we gave a probiotic (acidophilus) to help maintain balance of bacteria levels in the gut. We view this as preventative and he gets it everyday.
DHA: There is much research out today about how we all do not eat enough omega 3 rich foods in our diet. We use omega 3 rich oils in cooking (olive, walnut, canola, flax) and supplement with about 250 mg of Nordic Naturals DHA Strawberry flavor into applesauce or something else they like. We try to add ground flax seeds to smoothies, offer nuts with omega 3, and buy the eggs which are rich in omega 3.
GSH: Some people have seen tremendous results by adding oral GSH to their diet. CF people have an issue with releasing GSH out of the cells and adding a supplement can be helpful. We use 200 mg of GSH from TheraNaturals...there are other brands but I'm not sure what they are.
Tumeric: This spice has been well documented at helping reduce inflammation and is particularly helpful in CF. We just started this 2 weeks ago and are reducing enzymes this week since his stools have changed so much. I will be adding our research to the site below in the next few weeks.
Eating well: Makes sense, but loading the diet with poor quality fats and calories (too much dairy, animal fats without adequate complex carbs and fiber). The supplemental drinks which are recommended to CFers are loaded with corn syrup (very irritating to the gut) and sugar, not to mention artificial flavors. These things are not good for anyone not to mention someone who has digestive issues. These are not "good" calories and it may upset the system more than help in weight gain.
Making "power smoothies" is an alternative way to go. We do this and I've spoken to a mom who whose son has a GTube. He could not tolerate the commercial products (they discovered he had food allergies to corn syrup, wheat, dairy and other things). She began blending her own concoction of fresh fruits, veggies, healthy protein, and complex carbs) to put through the tube feeds and it has made a huge difference (started having an appetite again). VitaMix mixers is a great company for a super charged blender...they have a medical need program which offers significant discounts to people like us. Here is a link <a target=_blank class=ftalternatingbarlinklarge href="http://www.cfnutrition4life.com/cfnu/weblinks.php?cat_id=9">http://www.cfnutrition4life.co.../weblinks.php?cat_id=9</a> and a name of someone to call. I have some receipes on the site below but you can really have fun with it and include your kids in on what flavors to add (blueberries, tropical, strawberry and so on).
These changes are simple to try and can offer tremendous changes. It is basically an anti-inflammatory diet with extra calories coming more supportive foods.
Don't loose hope. Add just the probiotic and DHA first and observe them. Then try the GSH and observe some more. While you do this for a couple months...add more omega 3 to your cooking, try power smoothies here and there, try high protein pasta like Papadinini (lentil flour has a much protein as a steak), just keep it fun and see what happens.
Best wishes to better health,