Pure fat would probably be the best source of calories.

*Nuts & Seeds
*Fish & Free-Ranged Red Meats
*Poultry
*Olives
*Olive Oil, Flax Seed Oil, Macadamia Nut Oil, Hemp Seed Oil, Avocado Oil
*Sun-Dried Tomatoes
*Marinated in Olive Oil Vegetables
*Whole Eggs (or just yolks)