I have wondered about winter vs summer. In summer I think folks that are overweight only need about 20g of dietary fat and about 100g of protien and the rest should be carbohydrates which might be up to 1000g and whatever body fat they burn each day, which might be up to 500g. This is a very high carb diet but in terms of metabolism it still works out pretty balanced. Lean people cannot afford to burn as much body fat, or at least they will just have to replace it again when they get home so they might as well bring it with them.

In winter however I think even fat people need to consume more fat. I am not sure, but I think a balanced diet of carbs and fat helps keep the furnace going. That's what I keep telling myself anyway. I don't think I burn that much more in winter, but I think it is really important to have extra food anyways.

My current system:
Summer: 1 pound food/day, carbs and protien, little fat, to lose weight.
Spring/Fall: 2 pound/day, mostly carbs, some protien, little fat.
Winter: same as Spring/Fall, plus an extra pound of 50/50 fat/carbs.

My Spring/Summer/Fall food is stuff like:
Milk, Honey, Tea, Citrus, Oatmeal, Raisins, Dates, Almonds, Beef Jerky.

My extra winter food is stuff like:
Fruit and Nuts - More nuts than in Spring/Summer/Fall
Bacon and Scones - Fat to make the scones, scones to soak up more fat
Chocolate Chips and Raisins - They pack well together
Olive Oil and Honey - Simple way to pack extra emergency food.

I might pack an extra 500g of olive oil and 500g of honey, just to have an emergency ration in a dense package and keep it separate from the rest. The honey I am more inclined to dip into. The olive oil I am more inclined to use to experiment with oil lamps and wick stoves and stuff like that. If I bring bacon I don't really need olive oil to make scones. Olive oil is better for you of course, but what the heck. When your burning 6000 calories or more per day you can afford to live a little.