Dietary fats: discriminative partitioning for energy and synthesis of triacylglycerides

Fats and their component fatty acids provide important attributes of texture and flavour which are central to the perceived sensory properties of food. Fats have important roles in the intestinal absorption of fat soluble vitamins A, D, E and K and also produce satiety signals that regulate meal size. Fats, however, are likely best known for representing the greatest source of calories in the diet (e.g. approximately 9 kcal per gram for fat compared to 4 kcal per gram for protein and carbohydrates). Regulatory recommendations state that a maximum of 30% of calories derived from fat should be consumed by adults in the North American diet to assist in the prevention of chronic diseases (e.g. coronary heart disease and cancer). A growing body of evidence suggests that metabolic utilization of dietary fats is influenced by the overall composition of fatty acid comprising the fat; more specifically the size, isomeric configuration, degree of unsaturation and the esterified position on the glycerol molecule. Thus, qualitative factors of fat consumption in addition to the amount consumed may be a regulator of caloric balance. Various factors influencing the digestion, absorption and partitioning of dietary fat for energy utilization and synthesis of triacylglycerides are reviewed, with particular emphasis given to the methodology of evaluating the partition of fat for oxidation versus storage.