Sports Nutrition: Fat as an Energy Source During Exercise (PDF)

Because learning changes everything. ® Chapter 05 Fat: An Important Energy Source during Exercise Williams’ Nutrition for Health, Fitness and Sport Thirteenth Edition Eric S. Rawson, J. David Branch, Tammy J. Stephens...

Because learning changes everything. ® Chapter 05 Fat: An Important Energy Source during Exercise Williams’ Nutrition for Health, Fitness and Sport Thirteenth Edition Eric S. Rawson, J. David Branch, Tammy J. Stephenson © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  Dietary Fats Dietary fat is the nutrient of greatest concern to the American Heart Association because of the association of certain types of fat with coronary heart disease. Dietary fat is an important energy source for endurance-type sport events. © McGraw Hill, LLC 2  What are the different types of dietary fats? Triglycerides. Cholesterol. Phospholipids. Specific fatty acids: Omega-3 fatty acids. Omega-6 fatty acids. © McGraw Hill, LLC 3  What are triglycerides? An ester of glycerol (alcohol) and 3 fatty acids. © McGraw Hill, LLC 4  Types of Fatty Acids Access the text alternative for these images © McGraw Hill, LLC 5  What are some common foods high in fat content? Obviously high-fat content: Butter, oils, shortening, mayonnaise, margarine, and the visible fat on meat. Hidden fat: Whole milk, cheese, nuts, desserts, crackers, potato chips, and many commercially prepared foods. In general, animal foods tend to contain more total fat and saturated fat than plant foods. © McGraw Hill, LLC 6  Fatty Acids in Common Oils and Fats Note that fats are also typically rich in monounsaturated fatty acids (40–50% of total fatty acids). *Rich source of the omega-3 fatty acid alpha-linolenic acid (7% and 12% of total fatty acid content for soybean oil and canola oil, respectively). **Natural trans fatty acids in butter are not harmful. Access the text alternative for these images © McGraw Hill, LLC 7  How do I calculate the percentage of fat kcal in a food? Advertised percentage refers to the weight of the product, not its caloric content (water has no kcal). To determine the percentage of calories from fat in a product like the one below, divide calories from fat by total calories. Access the text alternative for these images © McGraw Hill, LLC 8  What are fat substitutes? Fat substitutes are designed to provide the taste and texture of fats, but without the kcal, saturated fat, or cholesterol. May be manufactured from carbohydrate, protein, or fat and may contain 0 to 4 kcal per gram. Some examples: Simplesse. Salatrim. Olestra. © McGraw Hill, LLC 9  What is cholesterol and what foods contain cholesterol? Cholesterol: Not a fat, but a sterol. Not an essential nutrient because it is manufactured in the liver. Cholesterol is found only in animal products: Protein foods including beef, pork, poultry, fish, shellfish, and eggs. Dairy products including milk, butter, cream cheese, and ice cream. Bread/cereal products prepared with animal products (that is, biscuits, pancakes, etc. made with milk and/or eggs). © McGraw Hill, LLC 10  What are phospholipids and what foods contain phospholipids? Not essential. The body can make them from triglycerides. Egg yolks provide substantial amounts of lecithin. Other good sources include liver, wheat germ, and peanuts. Access the text alternative for these images © McGraw Hill, LLC 11  How much fat and cholesterol do we need in the diet? We need fat for three reasons: To meet energy needs. To provide essential fatty acids. To provide essential fat-soluble vitamins. Important during growth and development years. © McGraw Hill, LLC 12  Dietary Fat: Dietary Reference Intakes 1 Total fat: An A M D R of 20 to 35 percent of daily energy intake. No R D A, A I, or U L have been set, but diets greater than 35 percent total fat are not recommended. Saturated fatty acids and trans fatty acids: No R D A, A I, or U L have been developed. Health professionals recommend maximum of 7 to 10 percent of daily energy needs. © McGraw Hill, LLC 13  Dietary Fat: Dietary Reference Intakes 2 Cis monounsaturated fatty acids: No R D A, A I, or U L developed. Some health professionals suggest these are good fats. Cis polyunsaturated fatty acids: Linoleic acid is an essential omega-6 fatty acid (A I: 17 g for adult males, 12 g for adult females). Alpha-linolenic acid is an essential omega-3 fatty acid (A I: 1.6 g for adult males, 1.1 grams for adult females). Cholesterol: By following a diet low in saturated fats, cholesterol intake will likely be between 100 and 300 mg/day. © McGraw Hill, LLC 14  Consequences of Excessive Consumption of Dietary Fat and Cholesterol Chronic diseases: May be linked to heart disease. May be linked to obesity. Impaired physical performance: May displace carbohydrates in the diet. May lead to excess caloric intake and body weight. May cause gastrointestinal distress as part of a pregame meal. © McGraw Hill, LLC 15  Metabolism and Function How does dietary fat get into the body? About 98 percent of dietary fat consists of triglycerides. About 2 percent consists of sterols and phospholipids. Bile salts and lipases digest dietary lipids into free fatty acids (F F As), glycerol, cholesterol, and phospholipids. Absorbed into intestinal cell; form a chylomicron, which enters the lymphatic system. Some fatty acids (from M C Ts) go directly to the liver. © McGraw Hill, LLC 16  Summary of Fat Digestion and Absorption Access the text alternative for these images © McGraw Hill, LLC 17  Schematic of a Lipoprotein Access the text alternative for these images © McGraw Hill, LLC 18  Absorption of Lipids Access the text alternative for these images © McGraw Hill, LLC 19  What happens to the lipid once it gets into the body? Circulate in the body as chylomicrons. Lipids deposited in body cells for storage as triglycerides. Fat or adipose cells. Muscle cells (IMTG—intramyocellular triacylglycerol). Liver continues to modify the composition of the lipoproteins. © McGraw Hill, LLC 20  What are the different types of lipoproteins? Very low-density lipoproteins (V L D L): Mainly triglycerides; provide fatty acids and glycerol to cells. Low-density lipoproteins (L D L): High proportion of cholesterol and phospholipids, but little triglycerides. Delivers cholesterol to cells. Small dense LDL of health concern. High-density lipoproteins (H D L): 40 to 50 percent protein. Transport cholesterol from cells to liver. Lipoprotein (a): Similar to L D L, in the upper L D L density range. © McGraw Hill, LLC 21  Content of Lipoproteins Access the text alternative for these images © McGraw Hill, LLC 22  Fat Metabolism Access the text alternative for these images © McGraw Hill, LLC 23  Can the body make fat from protein and carbohydrate? Fatty acids are polymers of acetyl C o A. Amino acids may be converted into acetyl C o A, which can then be converted into fat. Carbohydrates may be converted into fat via acetyl C o A. It is not what you eat, but how much, that determines if you will gain body fat. © McGraw Hill, LLC 24  What are the major functions of the body lipids? Structure: Component of cell membranes. Form myelin, an important component in the sheath covering nerve fibers. Function as insulators to conserve body heat and shock absorbers to protect organs. Metabolic regulation: Essential F F A involved in intracellular metabolic pathways. Cholesterol is part of some hormones. Adipose cells produce adipokines (adipocytokines), such as leptin, that influence metabolic processes. Eicosanoids possess local hormone-like properties. Energy source. © McGraw Hill, LLC 25  Fats as an Energy Source Fat produces energy only by aerobic processes. Fat provides about 60 percent or energy at rest. Triglycerides yield. Glycerol, which goes to the liver. FFA, which may be oxidized for energy. Ketones By-products of excess fatty acid metabolism. May be used for energy in cells. © McGraw Hill, LLC 26  How much total energy is stored in the body as fat? Fat is an efficient form of energy storage. 9 k cal per gram. Very little water content. Total amount of stored fat energy varies, but approximately 80,000 to 100,000 k cal in the average adult male with normal body fat. Most fat is stored in the adipose cells; about 2,500 to 2,800 k cal are stored in triglycerides within and between muscle cells. © McGraw Hill, LLC 27  Fats and Exercise Are fats used as an energy source during exercise? Fat energy sources. Plasma chylomicrons and triglycerides: minor source. Adipose cell triglycerides. Hormone-sensitive lipase released F F A. Increases serum F F A for delivery to muscle. Muscle cell triglycerides. Enzyme similar to H S L releases F F A. Use during exercise. Plasma F F A into muscles is increased during exercise. Epinephrine stimulates F F A release from adipose cell triglycerides to the muscle cell. © McGraw Hill, LLC 28  Fat as an Energy Source During Exercise Access the text alternative for these images © McGraw Hill, LLC 29  Fat Use During Exercise Mild exercise @ 25 percent V O2 max: About 80 percent or energy may come from fat. Most plasma FFA come from the adipose tissue. More intense exercise up to 65 percent V O2 max: Fats and carbohydrates appear to contribute equally to the energy expenditure. Plasma FFA and muscle triglycerides contribute equally to the energy derived from fats. High-intensity exercise ≥85 percent V O2 max: Carbohydrate is more important and fat use drops to ≤25 percent as muscle glycogen becomes the main source. In general, FFA oxidation decreases as carbohydrate oxidation increases with an increase in exercise intensity. © McGraw Hill, LLC 30  Fat Use During Exercise: Limiting factors Inadequate F F A mobilization from adipose tissue may limit delivery to the muscle. Suboptimal metabolism of intramuscular processes may limit fat oxidation. Increased carbohydrate oxidation may inhibit fatty acid oxidation. © McGraw Hill, LLC 31  Fat Use During Exercise: Dietary effects Carbohydrate intake decreases fat oxidation. Increased insulin may decrease lipolysis and fatty acid oxidation in muscle. Carbohydrate intake will help optimize endurance exercise performance. As carbohydrate levels diminish and F F A use increases, exercise intensity decreases. © McGraw Hill, LLC 32  Does sex influence the use of fats as an energy source during exercise? Some studies report females may oxidize more fat than males during submaximal exercise. Other research notes no difference in carbohydrate or fat metabolism during exercise in equally trained subjects. © McGraw Hill, LLC 33  What effect does exercise training have on fat metabolism during exercise? Exercise induces adaptations that enhance fat utilization and aerobic exercise performance. Increased expression of genes in the skeletal muscle that increase capacity for fat oxidation. With training, more energy used in exercise is derived from fat, sparing glycogen in muscle. Increased content and use of muscle triglycerides. © McGraw Hill, LLC 34  Fats: Ergogenic Aspects Strategies or supplements proposed to be ergogenic: High-fat diets. Fasting. Infusion of lipids into the bloodstream. Medium-chain triglycerides (MCTs). Lecithin. Glycerol. Omega-3 fatty acids or fish oil. Hydroxycitrate. Conjugated linoleic acid. Phosphatidylserine. Ketones. Caffeine. © McGraw Hill, LLC 35  High-Fat Diets Theoretical mechanism to help delay onset of fatigue. Elevated serum F F A levels and muscle triglyceride levels. Increase the percentage use of fat as an energy source during exercise. Spare the use of muscle glycogen. © McGraw Hill, LLC 36  Acute High-Fat Diets Acute high-fat diets (fat loading): Infuse a lipid solution, with heparin. Ingest a high-fat meal prior to exercise. Ingest a high-fat diet for 1 to 2 days prior to exercise. Research findings: Acute high-fat diets do not enhance aerobic endurance performance and may impair performance if they contribute to GI distress. Some research indicates consuming a high-fat diet for 1 to 2 days may impair performance in high- intensity exercise tasks. © McGraw Hill, LLC 37  Chronic High-Fat Diets Chronic high-fat diets: 50 percent or more energy from fat. Research findings: Athletes will increase their muscle triglyceride levels and may increase the use of fat and decrease use of carbohydrate during exercise. When an individual is placed on a chronic high-fat diet (1 week or more), the body adjusts its metabolism to use fats more efficiently. Metabolic improvements do not necessarily correlate with or guarantee performance improvements. © McGraw Hill, LLC 38  Chronic High-Fat Diets—Ergogenic Effect Few studies support an ergogenic effect of chronic fat loading. Increased exercise time to exhaustion at moderate intensity. Faster time in cycling time trial. Greater fat utilization and sparing of muscle glycogen. © McGraw Hill, LLC 39  Chronic High-Fat Diets—No Ergogenic Effect Well-controlled research suggests that chronic high- fat diets do not benefit endurance performance. No effect on cycling endurance or performance. Some evidence for enhanced ultra endurance cycling with a high-fat diet compared to a high- carbohydrate diet, though the main effects were not significant. In several studies, there was greater fat utilization and sparing of muscle glycogen. Studies of ketogenic diets have shown performance impairment. May impair cognitive function, speed, and mood. © McGraw Hill, LLC 40  High-Fat Diets and Weight Loss The long-term impact of a low-carbohydrate and high-fat (ketogenic) diet on weight loss in those with overweight or obesity unknown. When it comes to weight loss, kcal matters more than macronutrient distribution. Long-term effects on health outcomes (cancer and other diseases). © McGraw Hill, LLC 41  Does exercising on an empty stomach or fasting improve performance? Fasting may increase serum F F A availability and theoretically, increase fat oxidation, spare glycogen, and improve performance. If fasting reduces muscle glycogen or causes hypoglycemia, it may impair performance. Fasting may encourage greater weight loss, either through metabolic adaptations or reductions in appetite. © McGraw Hill, LLC 42  Can the use of medium-chain triglycerides (M C Ts) improve endurance performance or body composition? Theory as an ergogenic aid: Rapid absorption into portal circulation. Rapid uptake by mitochondria in muscle cells. Do not inhibit gastric emptying. May be absorbed rapidly in small intestine. May be oxidized at a rate similar to exogenous glucose. © McGraw Hill, LLC 43  Ergogenic Effects of M C Ts: Research Findings One study found that carbohydrate-M C T supplement improved performance by decreasing oxidation of muscle glycogen. Most studies have shown no benefits of supplementation with M C T or M C T combined with carbohydrate. Some report impaired performance with M C T supplementation. May also cause gastric distress in some individuals. © McGraw Hill, LLC 44  Is the glycerol portion of triglycerides an effective ergogenic aid? Theory as an ergogenic aid: Exogenous glycerol may be converted to glucose and be an efficient energy source during exercise. Research findings: Glycerol does not affect endurance performance. The rate of conversion by the liver may be too slow. © McGraw Hill, LLC 45  Omega-3 fatty acid and fish oil supplements Populations who eat a diet high in these fatty acids have decreased risk of cardiovascular disease. Potential anti-inflammatory effect of E P A and D H A. May enhance blood flow. May improve cognitive processing and reduce the damage and cognitive decline associated with concussion. May increase protein synthesis, decrease muscle soreness. No effect on glucose or lipid energy metabolism. No effect on aerobic endurance. © McGraw Hill, LLC 46  Can carnitine improve performance or weight loss? L-carnitine may help increase a specific enzyme that facilitates transport of long-chain fatty acids into mitochondria, which could increase fat oxidation. Research does not support an ergogenic effect of supplementation. © McGraw Hill, LLC 47  Carnitine Effects on Performance May increase plasma levels, but not muscle concentration of carnitine. No effect on fat oxidation. May reduce markers of metabolic stress and perceived muscle soreness, suggesting they promote recovery from resistance exercise. No effect on weight loss. © McGraw Hill, LLC 48  Can hydroxycitrate (H C A) enhance endurance performance? Theory as an ergogenic aid: Modify citric acid cycle metabolism to promote fatty acid oxidation. Research findings: Does not enhance endurance performance in humans. No effect on fat metabolism during exercise in either sedentary or endurance-trained cyclists. No benefit of H C A on weight loss, fat oxidation, or appetite. © McGraw Hill, LLC 49  Can conjugated linoleic acid (C L A) enhance exercise performance or weight loss? Theory as an ergogenic aid: Marketed as a means to decrease body fat and increase lean muscle mass in resistance-trained athletes. Research findings: Research with trained athletes is limited, but indicates C L A supplementation has no effect total body mass, fat mass, fat-free mass, or strength tests in resistance-trained athletes. Effects on health are discussed later in this chapter. © McGraw Hill, LLC 50  Can ketone supplements improve endurance performance? Some research with cyclists shows improved performance, while other research shows impaired performance. Poor gastrointestinal tolerance. @Fuse/Getty Images © McGraw Hill, LLC 51  What’s the bottom line regarding the ergogenic effects of fat-burning diets or strategies? Endurance exercise capacity is not improved with increased serum F F A availability and fat oxidation. High-fat diets may impair exercise performance. Difficult to adhere to a high-fat diet. © McGraw Hill, LLC 52  Dietary Fats and Cholesterol: Health Implications Dietary fat as a risk factor for chronic diseases may be associated with the amount and type of fat. A diet moderate in total fat reduces risk of chronic disease. The key is moderation. © McGraw Hill, LLC 53  How does cardiovascular disease develop? A number of cardiovascular diseases. Coronary heart disease (#1 cause of death): obstruction of the blood flow in the coronary arteries leading to heart attack. Stroke. Hypertensive disease. Rheumatic heart disease. Congenital heart disease. © McGraw Hill, LLC 54  The Heart and Coronary Arteries Access the text alternative for these images © McGraw Hill, LLC 55  Coronary Heart Disease Arteriosclerosis: Arterial walls thicken and lose their elasticity. Atherosclerosis: Associated with formation of plaque. Access the text alternative for these images © McGraw Hill, LLC 56  The Developmental Process of Atherosclerosis and Thrombosis Access the text alternative for these images © McGraw Hill, LLC 57  How do the different forms of serum lipids affect the development of atherosclerosis? Total cholesterol (lower is better). L D L-cholesterol (lower is better). H D L-cholesterol (higher is better). Triglycerides (lower is better). Cholesterol ratios: T C/H D L: 4.5 is average risk; lower is better. L D L/H D L: 3.5 is average risk; lower is better. © McGraw Hill, LLC 58  Serum Lipid Factors Associated with Increased Risk of Atherosclerosis High levels of total cholesterol. High levels of L D L-cholesterol. High levels of dense form of L D L-cholesterol. High levels of I D L-cholesterol. High levels of abnormal lipoprotein, lipoprotein (a). High levels of apolipoprotein B. High levels of triglycerides. Low levels of H D L-cholesterol. Low levels HDL of 2-cholesterol. Low levels of apolipoprotein A-I. © McGraw Hill, LLC 59  National Cholesterol Education Guidelines: Lipoprotein profile 1 Total cholesterol: Less than 200: Desirable. 200 to 239: Borderline high. 240 or above: High. H D L-cholesterol: Less than 40: Low. 60 or above: Protective. © McGraw Hill, LLC 60  National Cholesterol Education Guidelines: Lipoprotein profile 2 L D L-cholesterol: Less than 100: Optimal. 100 to 129: Near optimal. 130 to 159: Borderline high. 160 to 189: High. 190 and above: Very high. © McGraw Hill, LLC 61  National Cholesterol Education Guidelines: Lipoprotein profile 3 Triglycerides: Less than 150: Normal. 151 to 199: Borderline high. 200 to 499: High. 500 and above: Very high. © McGraw Hill, LLC 62  Can I reduce my serum lipid levels and possibly reverse atherosclerosis? Research suggests for each 1 percent reduction in serum LDL-cholesterol, there is a 1 percent reduction in risk of coronary heart disease. Healthier lifestyle. Diet. Exercise. Drugs. Statins inhibit an enzyme that regulates cholesterol. © McGraw Hill, LLC 63  D A S H Eating Plan Recommended changes using the D A S H eating plan to help lower blood pressure and L D L Source: NIH. Access the text alternative for these images © McGraw Hill, LLC 64  Guidelines on the Management of Blood Cholesterol 1. In all individuals, emphasize a heart-healthy lifestyle across the life course. 2. In patients with clinical A S C V D, reduce low-density lipoprotein cholesterol (L D L-C) with high-intensity statin therapy or maximally tolerated statin therapy. 3. In very high-risk A S C V D, use a L D L-C threshold of 70 mg/dl to consider addition of non-statins to statin therapy. Very high-risk includes a history of multiple major A S C V D events or 1 major A S C V D event and multiple high-risk conditions. 4. In patients with severe primary hypercholesterolemia (L D L-C level ≥190 mg/dl), without calculating 10-year A S C V D risk, begin high-intensity statin therapy. 5. In patients 40 to 75 years of age with diabetes mellitus and L D L-C ≥70 mg/dl, start moderate-intensity statin therapy without calculating 10-year A S C V D risk. 6. In adults 40 to 75 years of age evaluated for primary A S C V D prevention, have a clinician–patient risk discussion before starting statin therapy. 7. In adults 40 to 75 years of age without diabetes mellitus and with L D L-C levels ≥70 mg/dl, at a 10-year A S C V D risk of ≥7.5%, start a moderate-intensity statin if a discussion of treatment options favors statin therapy. 8. In adults 40 to 75 years of age without diabetes mellitus and 10-year risk of 7.5% to 19.9% (intermediate risk), risk-enhancing factors favor initiation of statin therapy (see No. 7). 9. In adults 40 to 75 years of age without diabetes mellitus and with L D L-C levels ≥70 mg/dL to 189 mg/dl, at a 10-year A S C V D risk of ≥7.5% to 19.9%, if a decision about statin therapy is uncertain, consider measuring C A C. 10.Assess adherence and percentage response to L D L-C–lowering medications and © McGraw Hill, LLC 65  Sensible Plan to Monitor the Effects of a Cholesterol-Lowering Diet Source: U.S Department of Health and Human Services. Access the text alternative for these images © McGraw Hill, LLC 66  Results of Switching to the Step 1 Diet Olga Nayashkova/Shutterstock Source: U.S. Department of Health and Human Services. Access the text alternative for these images © McGraw Hill, LLC 67  Essential Fatty Acids Polyunsaturated fatty acids should constitute about 10 percent of daily caloric intake. This should provide adequate amounts of omega-6 and omega-3 fatty acids. Omega-3 fatty acids (more important for the prevention of C H D than omega-6). Eicosapentaenoic acid (E P A). Docosahexaenoic acid (D H A). Found mainly in fish oils. © McGraw Hill, LLC 68  Grams of E P A and D H A in Fish (per 3 oz portion) and Fish Oils (per gram) >1 gram 0.5 to 1.0 gram