A little math shows the wisdom of carrying foods high in fat, such as nuts, oils and salami. Assuming a 3500 calorie day and a diet free from fat, one would need 875 grams of food. Go to a diet containing 40% fat and you can drop the weight per day to 640 grams, a savings of 235 grams or about 8 ounces -- 5 pounds on a 10 day Sierra trip.