ABSTRACT
Exercising muscle requires a signi™cant amount of energy to do work. Much of the energy required for exercising muscle is provided from stored forms of fat and carbohydrates. Although protein may also provide energy to working muscle, its contribution during exercise is considered negligible under most circumstances. Fat is present in abundance in the human body compared with carbohydrate stores, regardless of ™tness level and body-fat percentage. In fact, fat comprises the largest fuel reserve in the body, exceeding that of carbohydrate several fold (Horowitz and Klein 2000). Fat is also the ideal fuel for exercising muscle because it is stored not only in adipose
8.1 Introduction .................................................................................................. 139 8.2 Structure and Classi™cation of Dietary Fat .................................................. 140
8.2.1 Dietary Fat Structure ........................................................................ 140 8.2.2 Classi™cation of Dietary Fats ........................................................... 140 8.2.3 Dietary Fat Structure Impacts Health ............................................... 141
8.3 Fat Metabolism ............................................................................................. 142 8.3.1 Digestion and Absorption ................................................................. 142 8.3.2 Transport and Storage ....................................................................... 143 8.3.3 Fatty-Acid Transport ......................................................................... 143 8.3.4 Fatty-Acid Oxidation ........................................................................ 144
8.4 Fat Metabolism during Exercise ................................................................... 144 8.4.1 Adipose Tissue .................................................................................. 145 8.4.2 Circulating Fatty Acids ..................................................................... 146 8.4.3 Intramuscular Triglyceride ............................................................... 146
8.5 Exercise Effects ............................................................................................ 146 8.5.1 Effect of Exercise on Fat Metabolism .............................................. 146 8.5.2 Effect of Exercise on Cholesterol ..................................................... 147
8.6 Dietary Recommendations ........................................................................... 148 8.6.1 Fat Sources in the Diet ...................................................................... 149 8.6.2 High-Fat Diets and Fat Loading ....................................................... 153 8.6.3 Training Table ................................................................................... 153
8.7 Conclusion .................................................................................................... 154 References .............................................................................................................. 154
tissue, but in muscle, as intramuscular triglycerides, as well as circulating in the blood carried by protein carriers called lipoproteins. Fat contains more than twice as much energy per gram as carbohydrates and is stored in the absence of water, unlike carbohydrates, making it far more ef™cient per unit weight than its counterparts for energy during exercise (Jeukendrup et al. 1998b). Taken together, it is easy to see how fat is of great importance to exercising muscle.
