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Transcript
Nutrition and Energy Metabolism in Exercise 1 Energy for Sport: Preferred Fuels and Overall Energy Requirements Photo courtesy of http://www.bodylab.co.nz/VO2max/VO2max.htm 2 How Do We Go From Eating Food to Powering Muscles? Digestion of food Absorption of nutrients from intestine into blood Uptake of nutrients from blood into muscle cells Use of nutrients to generate adenosine triphosphate (ATP)— the energy currency of cells: Adenine (base) 7.3 kcal/mola Adenosine Ribose (sugar) a High energy bonds in red. Adapted from http://commons.wikimedia.org/wiki/File:ATP_structure_revised.png 3 Pathways for Your Body to Generate ATP From Nutrients Oxygen Required Process Duration ATP Yield Pathways Substrate-level phosphorylation No Quick Small Creatine phosphate, anaerobic glycolysis, 1 step in the tricarboxylic acid (TCA) cycle Oxidative phosphorylation Yes Long Large Aerobic glycolysis, fatty acid metabolism Process Which process is dominant during exercise? – Depends on oxygen availability – Affected by training and nutrient stores available 4 Creatine Phosphate Pathway Creatine stores may be a limiting factor for adenosine triphosphate (ATP) synthesis during explosive, high-intensity activities Creatine plays a role in maximal effort lasting up to 10 sec Key dietary issues include maintaining and maximizing creatine stores in muscle 5 The Creatine Phosphate Pathway and Breakdown of Creatine Phosphate to Creatinine CPK or CK 3 different types (isoforms) of creatine kinase (CK) – CK-BB, or CK-1 (brain, lung) – CK-MB, or CK-2 (cardiac) – CK-MM, or CK-3 (skeletal muscle) Net result from creatine phosphate breakdown: 1 ATP Abbreviations: ADP, adenosine diphosphate; ATP, adenosine triphosphate; CPK, creatine phosphokinase. Reprinted from Smith C, et al. Marks’ Basic Medical Biochemistry: A Clinical Approach. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2005:870-871. 6 Aerobic and Anaerobic Glycolysis Anaerobic Aerobic Glycogen Dietary Glucose Glucose (6-carbon) •2 ATP required (1 if starting from glycogen •4 ATP generated from SLP •2 NADH + H+ enter electron transport chain to produce ATP Net result: 5-7.5 ATP from SLP and NADH + H+ Pyruvate (3-carbon) •2 ATP required (1 if starting from glycogen) •4 ATP generated from SLP •2 NADH + H+ used to form lactate from pyruvate Pyruvate (3-carbon) Abbreviations: ATP, adenosine triphosphate, H+, hydrogen; NADH, reduced form of nicotinamide adenine dinucleotide; SLP, substrate-level phosphorylation. Data from Salway JG. Metabolism at a Glance. 3rd ed. Maldern, MA: Blackwell Publishing; 2004:20-21. Net result: and 2-3 ATP 7 Hydrogen and electron carriers: an important link between B-vitamins and energy production Nicotinamide adenine dinucleotide (NAD) – The B-vitamin niacin is part of its structure – Can donate hydrogen and electrons for synthesis of adenosine triphosphate (ATP) • Reduced form is symbolized as NADH + H+ • Worth 2.5 ATP when entering electron transport system Flavin adenine dinucleotide (FAD) – The B-vitamin riboflavin is part of its structure – Can donate hydrogen and electrons for synthesis of ATP • Reduced form is FADH2 • Worth 1.5 ATP when entering electron transport system 8 ATP Yields: Glucose to Pyruvate Starting from… Dietary Glucose Glycogen 2 3 4.5 4.5 3 3 2 3 5 to 6.5 6 to 7.5 Net ATP by SLP Oxidative phosphorylation (2 NADH +H+) ATP yield (malate shuttle) ATP yield (G-P shuttle) OR ATP yield (anaerobic) ATP yield (aerobic) Abbreviations: ATP, adenosine triphosphate; H+, hydrogen; G-P, glucose to pyruvate; NADH, reduced form of nicotinamide adenine dinucleotide; SLP, substrate-level phosphorylation. Data from Salway JG. Metabolism at a Glance. 3rd ed. Maldern, MA: Blackwell Publishing; 2004:20-21. 9 Fate of Pyruvate Aerobic – Enters mitochondria – Converted to acetyl coenzyme A (CoA) • This reaction generates 1 NADH + H+ • Thiamin is a coenzyme for pyruvate dehydrogenase (PDH) – Acetyl fragment enters tricarboxylic acid (TCA) cycle Anaerobic – Converted to lactate using hydrogen and electrons donated from NADH + H+ Abbreviations: H+, hydrogen; NADH, reduced form of nicotinamide adenine dinucleotide. 10 ATP Yields: Pyruvate to Acetyl CoA This conversion is mediated by PDH, a thiamin-dependent enzyme Each of the 2 pyruvate molecules from glucose metabolism can be converted to acetyl CoA Pyruvate NAD+ CO2 NADH + H+ 2 NADH + H+ × 2.5 ATP ea. Dietary Glucose Glycogen 5 5 Acetyl CoA Abbreviations: ATP, adenosine triphosphate; CO2, carbon dioxide; CoA, coenzyme A; H+, hydrogen; NAD, nicotinamide adenine dinucleotide; PDH, NADH, reduced form of NAD; PHD, pyruvate dehydrogenase. Data from Salway JG. Metabolism at a Glance. 3rd ed. Maldern, MA: Blackwell Publishing; 2004:21. 11 Fate of NADH + H+ Aerobic – Can enter the mitochondrion – Donates hydrogen and electrons to the electron transport system (ETS) for synthesis of adenosine triphosphate (ATP) Anaerobic – Donates hydrogen and electrons to pyruvate to form lactate (enzyme is lactate dehydrogenase [LDH]) Abbreviations: H+, hydrogen; NADH, reduced form of nicotinamide adenine dinucleotide. 12 Lactate Accumulation and Lactate Threshold (Trained vs Untrained Subjects) VO2 max, % Abbreviation: VO2 max, peak exercise oxygen consumption. Reprinted from McArdle WD et al. Exercise Physiology: Nutrition, Energy, and Human Performance, 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010:163. 13 Fate of Lactate: Not the bad guy it was always made out to be! Lactate accumulates in blood as rate of muscle production exceeds rate of clearance/utilization Lactate formation is NOT the cause of the lowering of muscle pH that occurs during exercise – Lactate accumulation occurs simultaneously with other factors that do lower muscle pH (i.e., cause accumulation of H+) • One example is the release of H+ that occurs when ATP is hydrolyzed for energy During recovery or slowing of exercise, a portion of lactate can be converted first to pyruvate and then back to glucose (the Cori cycle) – Occurs mainly in the liver 14 The Tricarboxylic Acid (TCA) Cyclea Inner matrix of mitochrondrion NADH + 2-carbon acetyl CoA fragment NAD+ Oxaloacetate (4 C) H+ Citrate (6 C) Fumarate (4 C) FAD FADH2 Succinate (4 C) Isocitrate (6 C) GDP NAD+ GTP NADH + H+ Succinyl CoA (4 C) ATP NAD+ NADH + H+ CO2 -ketoglutarate (5 C) CO2 Net result: 1 turn of the cycle; 3 NADH, 1 GTP, 1 FADH2, and 2 molecules of CO2 released a Also known as the Krebs or citric acid cycle. Abbreviations: ATP, adenosine triphosphate; C, carbon; CO2, carbon dioxide; CoA, coenzyme A; FAD, flavin adenine dinucleotide; FADH, reduced form of FAD; GDP, guanosine diphosphate; GTP, guanosine triphosphate. NAD, nicotinamide adenine dinucleotide; NADH, reduced form of NAD. Reprinted from Alberts B, et al. Essential Cell Biology, 2nd ed. London; Garland Science; 2004:chapt 13. 15 The Electron Transport System (ETS) Intermembrane space Inner membrane Mitochondrial matrix Abbreviations: ADP, adenosine diphosphate; ATP, adenosine triphosphate; e–, electron; FAD, flavin adenine dinucleotide; H+, hydrogen; NAD, nicotinamide adenine dinucleotide; O, oxygen; P, phosphate. Reprinted from http://student.ccbcmd.edu/~gkaiser/biotutorials/energy/fg5.html. 16 ATP Yields: TCA Cycle TCA cycle (mitochondria) subtotal Acetyl CoA oxaloacetate 3 NADH + H+ 1 FADH2 1 GTP 2 CO2 citrate Dietary Glucose Glycogen 6 NADH + H+ × 2.5 ATP ea. 15 15 2 FADH2 × 1.5 ATP ea. 3 3 2 GTP × .75 ATP ea. (SLP) 1.5 1.5 SUBTOTAL 19.5 19.5 Abbreviations: ATP, adenosine triphosphate; CO2, carbon dioxide; CoA, coenzyme A; FADH2, reduced form of flavin adenine dinucleotide; GTP, guanosine triphosphate; H+, hydrogen; NADH, reduced form of nicotinamide adenine dinucleotide; SLP, substrate-level phosphorylation; TCA, tricarboxylic acid. Data from Salway JG. Metabolism at a Glance. 3rd ed. Maldern, MA: Blackwell Publishing; 2004:21. 17 Energy Metabolism of Fatty Acids Digestion and absorption of triglycerides – Hydrolysis of triglyceride by lipases – Medium-chain fatty acids: Absorbed directly into blood – Long-chain fatty acids: Absorbed first into lymphatic system, then blood Fatty acids enter cells, join with CoA (activation), and enter mitochondria – Long-chain fatty acids: Require a carnitine transporter to get into mitochondria Process of cutting the fatty acid down into successive 2-carbon units (each becomes acetyl CoA) – Called β-oxidation Acetyl CoA units are then metabolized the same way via TCA cycle and ETS as previously described for glucose Abbreviations: CoA, coenzyme A; ETS, electron transport system; TCA, tricarboxylic acid. 18 Medium chain triglycerides/fatty acids Medium chain fatty acids (~10-12 carbons or less) have unique properties compared with long chain fatty acid regarding their absorption and metabolism – Absorbed directly into the portal blood versus lymphatics (more water soluble) • Transported directly to liver following absorption – Do not require a transporter (e.g., carnitine transporter) to enter the mitochondria for oxidation – Metabolized more like a carbohydrate than a fat Potential alternate energy source for working muscles, but a key problem is getting these fatty acids to peripheral tissues – Potential solution: Structured triglyceride – Alters position of medium chain fatty acids on glycerol backbone – Greater inclusion in lymphatics for transport to periphery Putting It All Together: Glucose and Fatty Acid Energy Metabolism Glucose Cytosol Glycogen ATP Activated fatty acid Anaerobic Pyruvate LDH Fatty acid Lactate Aerobic Activated fatty acid Pyruvate PDH Acetyl CoA TCA cycle Mitochondria β-oxidation NADH + H+ FADH2 ETS Abbreviations: ATP, adenosine triphosphate; CoA, coenzyme A; ETS, electron transport system; FADH 2, reduced form of flavin adenine dinucleotide; H+, hydrogen; LDH, lactate dehydrogenase; NADH, reduced from of nicotinamide adenine dinucleotide; PDH, pyruvate dehydrogenase; TCA, tricarboxylic acid. 20 21 Putting It All Together: ATP Yields per Mole Glucosea Starting from Dietary Glucose Shuttle Malate G-P Malate G-P 2 2 3 3 4.5 3 4.5 3 5 5 5 5 6 NADH + H+ 15 15 15 15 2 FADH2 3 3 3 3 1.5 1.5 1.5 1.5 31 29.5 32 30.5 Glycogen Glucose to pyruvate SLP 2 NADH + H+ Pyruvate to acetyl CoA 2 NADH + H+ Acetyl CoA to CAC/ETS 2 GTP ATP TOTALS a ATP yields assuming optimal function of ETS. In reality, however, electron leakage occurs. Abbreviations: ATP, adenosine triphosphate; CoA, coenzyme A; ETS, electron transport system; FADH 2, reduced form of flavin adenine dinucleotide; G-P, glucose to pyruvate; GTP, guanosine triphosphate; H+, hydrogen; NADH, reduced form of nicotinamide adenine dinucleotide; SLP, substrate-level phosphorylation; TCA, tricarboxylic acid. Data from Salway JG. Metabolism at a Glance. 3rd ed. Maldern, MA: Blackwell Publishing; 2004:21. Putting It All Together: ATP Yields With Palmitate Palmitate is a 16-carbon, saturated fatty acid (16:0) ATP -oxidation (7 cycles) 1 NADH + H+/cycle × 7 cycles × 2.5 ATP/NADH + H+ 17.5 1 FADH2/cycle × 7 cycles × 1.5 ATP/FADH2 10.5 Acetyl CoA to TCA cycle (8 acetyl CoA) 3 NADH + H+/acetyl CoA × 8 acetyl CoA × 2.5 ATP/NADH + H+ 60 1 FADH2/acetyl CoA × 8 acetyl CoA × 1.5 ATP/FADH2 12 1 GTP/acetyl CoA × 8 acetyl CoA × 0.75 ATP/GTP 6 Activation of fatty acid –2 TOTAL 104 Abbreviations: ATP, adenosine triphosphate; CoA, coenzyme A; FADH2, reduced form of flavin adenine dinucleotide; GTP, guanosine triphosphate; H+, hydrogen; NADH, reduced form of nicotinamide adenine dinucleotide; TCA, tricarboxylic acid. Data from Salway JG. Metabolism at a Glance. 3rd ed. Maldern, MA: Blackwell Publishing; 2004:39. 22 Key Summary Points Metabolism of carbohydrate – Pro: Can support high-intensity exercise because glycolysis can occur without oxygen – Cons: Lactate build-up occurs; carbohydrate stores are very limited in the body relative to fat Metabolism of fat – Pros: ATP yields are very large for fatty acids (generally > 100 ATP/mol) versus glucose (≤ 32 ATP/mol); very dense energy reserve (3,500 kcal = 1 lb body fat) – Con: Requires oxygen and the process of metabolizing fats is not as quick as glycolysis; training required to enhance the body’s ability to access fat for energy during exercise Abbreviation: ATP, adenosine triphosphate. 23 Do We Use Protein for Energy? We can, but it is generally not desirable to do so – Maybe 5% to 10% of total cost of exercise activity – Mainly branched-chain amino acids (leucine, isoleucine, valine) – Carbohydrate depletion increases amino acid oxidation Must remove the nitrogen (amino group) and excrete it (mainly as urea) before metabolizing the carbon skeleton Amino acids are typically either glucogenic (carbon skeletons convert to glucose) or ketogenic (carbon skeletons convert to acetyl CoA like fats do) Abbreviation: CoA, coenzyme A. 24 How Does the Body Decide What to Burn for Fuel at a Given Time? Influenced by a number of factors – – – – – Intensity of exercise and oxygen availability Fuel stores available (carbohydrate depletion) Hormonal influences (insulin, epinephrine, cortisol) Training effects regarding ability to deliver and use oxygen Muscle fiber make-up 25 Effect of Exercise Intensity on Substrate Oxidation in Trained Men cal/kg/min 300 Muscle glycogen Muscle triglycerides Plasma FFA Plasma glucose 200 100 0 25 65 85 VO2 max, % Abbreviations: FFA, free fatty acid; VO2 max, peak exercise oxygen consumption. Reprinted from Romijn JA. Am J Physiol. 1993;265(3 Pt 1):E380-E391. 26 27 Classification of Human Skeletal Muscle Fiber Types Muscle fiber type Type I fibers Type IIa fibers Type IIx fibers Type IIb fibers Contraction time Slow Moderately fast Fast Very fast Resistance to fatigue High Fairly high Intermediate Low Aerobic Long-term anaerobic Short-term anaerobic Short-term anaerobic Hours < 30 minutes < 5 minutes < 1 minute Force production Low Medium High Very high Mitochondrial density High High Medium Low Capillary density High Intermediate Low Low Oxidative capacity High High Intermediate Low Glycolytic capacity Low High High High Major storage fuel Triacylglycerol Creatine phosphate, glycogen Creatine phosphate, glycogen Creatine phosphate, glycogen Activity used for Maximum duration of use Adapted from McArdle WD et al. Exercise Physiology: Nutrition, Energy, and Human Performance, 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010:371. Energy Requirements of Athletes It is very difficult to estimate the energy requirements of different athletes – Measuring kcals burned during physical activity is the most difficult • Motion detectors, heart rate, portable spirometry, doubly-labeled water – Growth requirements in younger athletes complicate the issue – Trying to match reported energy intake with weight maintenance is also problematic • Energy intake is frequently underreported in studies Reported energy intakes of athletes are highly variable – Within athletes in a given sport • Stage of training is an important factor – Between athletes in different sports 28 Reported Energy Intake of Athletes Athlete kcal/day kcal/kg/day Study 4,140 ± 504 46 DeWijn et al1 4,211 ± 227 48 Papadokonstantaki et al2 4,176 ± 302 53 Simonsen et al3 5,800 57 Strauzenberg et al4 5,267 ± 315 62 Short and Short5 6,560 75 Ntimof6 1,706 ± 421 56 Benardot et al7 2,580 63 Ntimof6 Elite 1,935 ± 398 70 Grandjean8 Amateur 1,637 ± 199 74 Chen9 Elite 2,298 ± 326 51 Male rowers Female gymnasts 1. De Wijn FJ, et al. Bibl Nutr Dieta. 1979;(27):143-148. 2. Papadokonstantaki M, et al. World Rev Nutr Diet. 1993;71:183-184. 3. Simonsen JC, et al. J Appl Physiol. 1991;70:1500-1505. 4. Strauzenberg SE, et al. Bibl Nutr Dieta. 1979;(27):133-142. 5. Short SH, Short RW. J Am Diet Assoc. 1983;82(6):632-645. 6. Ntimof F. Sports Nutrition. Jusantor, Sofie, 1987. 7. Benardot D, et al. J Am Diet Assoc. 1989;89(3):401-403. 8. Grandjean AC. Am J Clin Nutr. 1989;49(5 suppl):1070-1076 9. Chen JD, et al. Am J Clin Nutr. 1989;49(5 suppl):1084-1089. Data from Pavlou KN. Energy needs of the elite athlete. World Rev Nutr Diet. 1993;71:9-20. 29 Reported Energy Intake of Athletes (cont’d) Athlete kcal/day kcal/kg Study Female distance runners 1,931 - 2,489 McArdle et al1 Male distance runners 3,034 - 3,170 McArdle et al1 Ziegler et al2 Elite figure skaters Men 2,329 (57% carb) Women 1,545 (60% carb) 36 Female swimmers (taper, collegiate) 2,275 (63% carb) 34 Ousley-Pahnke et al3 Ultra-endurance runner 10,743 (95% carb) 168 Rontoyannis et al4 Wolinsky5 Bodybuilder Offseason 8,159 (no carb) 78 Precompetition 2,624 (4% carb) 29 1. Mc Ardle WD, et al. Sports and Exercise Nutrition, 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:chapt 7:223. 2. Ziegler P, et al. J Am Diet Assoc. 2001;101(3):319-325. 3. Ousley-Pahnke L, et al. J Am Diet Assoc. 2001;101(3):351-354. 4. Rontoyannis GP, et al. Am J Clin Nutr. 1989;49(5 suppl):976-979. 5. Wolinsky I. Nutrition in Exercise and Sport, 3rd ed. Boca Raton, FL: CRC Press; 1997. Adapted from Mc Ardle WD, et al. Sports and Exercise Nutrition, 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:chapt 7:223. 30 Components of Energy Expenditure Basal Metabolic Rate (BMR) – Energy needed to maintain vital body functions – Typically measured after 8 hours of rest, 12 to 18 hours of fasting – Almost the same as Resting Energy Expenditure (REE) • REE measured 3 to 4 hours post-absorptive • Within 10% of the BMR – Equals roughly 3.5 mL O2 consumed/kg/min • This is called 1 metabolic equivalent (MET) • Exercise intensity often is measured as a multiple of resting (eg, 10 METS) – Affected by surface area, the amount of fat-free mass, and metabolic efficiency (brown fat) Abbreviation: O2, oxygen. 31 Components of Energy Expenditure (cont’d) Thermic Effect of Exercise (TEE) – Energy expended during voluntary physical activity – Most variable component • Can range from 0 to 50% or more of total energy requirement (TER) – For a 70-kg person cycling at 15 mph, energy expenditure is ~7× BMR, or 7 METS Diet-Induced Thermogenesis (DIT) – kcals needed to digest, absorb, and store nutrients – About 5% to 10% of BMR Non-exercise Activity Thermogenesis (NEAT) – kcals burned during behaviors like fidgeting – Can sometimes account for 400 to 500 kcal/d Abbreviations: BMR, basal metabolic rate; METS, metabolic equivalents. 32 Estimating Energy Expenditure Can measure TER via doubly labeled water – Expensive Can measure BMR via indirect calorimetry and multiply by factors – Must have indirect calorimeter – 1 L O2 consumed 5 kcals Can determine EER using equations – US Institute of Medicine (IOM) has developed equations for Estimated Energy Requirement (EER) based on age, sex, height, weight, and physical activity level1 – They have 7 separate DRI volumes for energy and various nutrients • All can be read online (tedious) or purchased as individual hard copies • The summary hard copy (condensed version) of all the DRI reports can be helpful Abbreviations: BMR, basal metabolic rate; DRI, dietary reference intake; TER, total energy requirement. 1. Institute of Medicine of the National Academies. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. National Academies Press: Washington DC. 33 IOM Physical Activity Levels (PAL) and Coefficients (PA) Physical Activity Coefficients (PA Values) for Use in EER Equations Sedentary Low Active Active a (PAL 1.0-1.39) (PAL 1.4-1.59) (PAL 1.6-1.89) Plug one of these values into the EER Boys 3-18 y equation Girls 3-18 y Men 19 y + Women 19 y + Typical daily living activities (eg, household tasks, walking to the bus) 1.00 1.00 Typical daily living activities PLUS 30-60 minutes of daily moderate activity (eg, walking at 5-7 km/h) 1.13 1.16 Typical daily living activities PLUS at least 60 minutes of daily moderate activity 1.26 1.31 Very Active (PAL 1.9-2.5) Typical daily living activities PLUS at least 60 minutes of daily moderate activity PLUS an additional 60 minutes of vigorous activity or 120 minutes of moderate activity 1.42 1.56 1.00 1.00 1.11 1.12 1.25 1.27 1.48 1.45 a PAL is a multiple of basal energy expenditure and is used to determine the applicable PA on this table. Abbreviations: ADL, activities of daily living, EER, estimated energy requirement; IOM, Institute of Medicine; PA, physical activity coefficient; PAL, physical activity level. Reprinted from Institute of Medicine of the National Academies. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. National Academies Press: Washington DC; 2006:84. 34 IOM Equations for EER Equations to Estimate Energy Requirement Infants and Young Children Estimated Energy Requirement (kcal/day) = Total Energy Expenditure + Energy Deposition 0-3 months EER = (89 × weight [kg] – 100) + 175 4-6 months EER = (89 × weight [kg] – 100) + 56 7-12 months EER = (89 × weight [kg] – 100) + 22 13-35 months EER = (89 × weight [kg] – 100) + 20 Children and Adolescents 3-18 years Estimated Energy Requirement (kcal/day) = Total Energy Expenditure + Energy Deposition Boys 3-8 years EER = (88.5 – (61.9 × age [y] + PAb × [(26.7 × weight [kg]) + (903 × height [m])] + 20 9-18 years EER = (88.5 – (61.9 × age [y] + PA × [(26.7 × weight [kg]) + (903 × height [m])] + 25 Girls 3-8 years EER = (135.3 – (30.8 × age [y] + PA × [(10.0 × weight [kg]) + (934 × height [m])] + 20 9-18 years EER = (135.3 – (30.8 × age [y] + PA × [(10.0 × weight [kg]) + (934 × height [m])] + 25 Adults 19 years and older Estimated Energy Requirement (kcal/day) = Total Energy Expenditure Men EER = 662 – (9.53 × age [y]) + PA × [(15.91 × weight [kg]) + 539.6 × height [m])] Women EER = 354 – (6.91 × age [y]) + PA × [(9.36 × weight [kg]) + (726 × height [m])] Pregnancy Estimated Energy Requirement (kcal/day) = Nonpregnant EER + Pregnancy Energy Deposition 1st trimester EER = Nonpregnant EER + 0 2nd trimester EER = Nonpregnant EER + 340 3rd trimester EER = Nonpregnant EER + 452 Lactation Estimated Energy Requirement (kcal/day) = Nonpregnant EER + Milk Energy Output – Weight Loss 0-6 months postpartum EER = Nonpregnant EER + 500 – 170 7-12 months postpartum EER = Nonpregnant EER + 400 – 0 Abbreviations: EER, estimated energy requirement; IOM, Institute of Medicine; PA, physical activity coefficient. Reprinted from Institute of Medicine of the National Academies. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. National Academies Press: Washington DC; 2006:82. 35 Example of Energy Requirement Calculation Very active 20-year-old female; 132 lb (60 kg); 5’, 5” tall (1.4 m) – PA = 1.45a EER = 354 – (6.91 × age [yr]) + PA × [(9.36 × weight [kg]) + (726 × height [m])]b EER = 354 – (6.91 × 20) + 1.45 × [(9.361 × 60) + (726 × 1.4)] EER = 354 – 138.2 + 1.45 × [561.66 + 1,016.4] EER = 215.8 + [2,289.18] EER = 2,504 kcal a From IOM PA table.1 From IOM EER table.1 Abbreviations: EER, estimated energy requirement; IOM, Institute of Medicine; PA, physical activity coefficient. 1. Institute of Medicine of the National Academies. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. National Academies Press: Washington DC; 2006:537. b 36 Example of Simplified Energy Requirement Calculation Previous calculation to estimate EER is lengthy, cumbersome Simplified calculation to estimate TER: TER = weight (kg) × 40 to 60 kcal/kg/day Very active 20-year-old female; 132 lb (60 kg); 5’, 5” tall (1.4 m) Using 40 kcal/kg: TER = 60 × 40 kcal/kg = 2,400 kcal/day Using 45 kcal/kg: TER = 60 × 45 kcal/kg = 2,700 kcal/day Using 50 kcal/kg: TER = 60 × 50 kcal/kg = 3,000 kcal/day Using 60 kcal/kg: TER = 60 × 60 kcal/kg = 3,600 kcal/day Abbreviations: EER, estimated energy requirement; TER, total energy requirement. 37 Energy Expenditure in Athletes: Considerations Without direct measurement of energy expenditure, equations offer only a rough estimate Monitor weight of the athlete on a particular energy intake and adjust the energy intake accordingly depending on whether weight gain, maintenance, or loss is desired – Most people, including athletes, underreport food intake and over report physical activity when questioned 1 lb body fat 3,500 kcal For weight loss, target gradual weight loss when possible (1 lb/week is a good goal) – Avoids loss of lean tissue that can happen with more rapid weight loss – Loss of 1 lb/week = 500 kcal/day deficit • For example, reduce food intake by 250 kcal/day and increase physical activity by 250 kcal/day 38 Supplementary Slide on ATP and muscle contraction 39 ATP Role in Muscle Contraction Abbreviations: Ach, acetylcholine; ADP, adenosine diphosphate; ATP, adenosine triphosphate; Ca 2+, calcium. Reprinted from McArdle WD, et al. Exercise Physiology: Nutrition, Energy, and Human Performance, 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010:370. 40