THE IMPORTANCE OF DIETARY ANIMAL FAT1
In contrast, the modern human uses two classes of food to provide energy for life functions; carbohydrates yield glucose, and fats supply fatty acids. Despite the fact that glucose serves as the usual and ready source of energy for the body, long-term sustained energy depends on fatty acids. Fatty acids are a much more efficient fuel than glucose. They contain twice the energy per unit weight and they are stored more compactly. Under normal conditions, the body uses both fuels alternately depending on time from last meal.