a great supplement I've found to boost calories and which is actually intended in part as a prerequisite to sports/activity is Alpha PMX--a complete vitamin and mineral/meal supplement or even replacement if necessary. I take it a lot. 50g is 180 cals. It tastes ok too, .. not delicious or anything, but definitely more than bearable! It's completely non food derived --I was looking for something hypoallergenic so it's ideal in this way. It's helped me immeasurablly because my diet's so limited and I too like to keep active. The only drawback is it's not cheap.
The website to check out is www.alphanutrition.com They actually do a whole load of products that are quite interesting.. but because of cost, I just get the PMX and think it's sufficient.
Hope this helps
I'm about to launch into bowel, parasite etc cleansing. I've a lot of food allergies and reactions to sugars/carbs. Am bit at a loss with the conventional doctors who don't seem to have any answers.