Nutrition and Energy Metabolismin Exercise

1

Energy for Sport: Preferred Fuels and Overall Energy Requirements

2

Photo courtesy of

http://www.bodylab.co.nz/VO2max/VO2max.htm

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:

3

Adenine (base)

Ribose (sugar)

Adenosine

7.3 kcal/mola

a High energy bonds in red.Adapted from http://commons.wikimedia.org/wiki/File:ATP_structure_revised.png

Pathways for Your Body to Generate ATP From Nutrients

Which process is dominant during exercise?– Depends on oxygen availability– Affected by training and nutrient stores available

4

ProcessOxygen

RequiredProcess

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

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

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)

6

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.

CPK or CK

Net result from creatine phosphate breakdown:1 ATP

Aerobic and Anaerobic Glycolysis

7

Glucose (6-carbon)

Pyruvate(3-carbon)

Pyruvate(3-carbon)

Glycogen Dietary Glucose

•2 ATP required (1 if starting from glycogen)•4 ATP generated from SLP•2 NADH + H+ used to form lactate from pyruvate

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:and2-3 ATP

•2 ATP required (1 if starting from glycogen•4 ATP generated from SLP•2 NADH + H+ enter electron transport chain to produce ATP

AnaerobicAerobic

Net result:5-7.5 ATP from SLP and NADH + H+

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

9

Dietary Glucose Glycogen

Net ATP by SLP 2 3

Oxidative phosphorylation (2 NADH +H+)

ATP yield (malate shuttle) 4.5 4.5

ATP yield (G-P shuttle) 3 3

ATP yield (anaerobic) 2 3

ATP yield (aerobic) 5 to 6.5 6 to 7.5

OR

Starting from…

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.

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+

10Abbreviations: H+, hydrogen; NADH, reduced form of nicotinamide adenine dinucleotide.

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

11

Pyruvate

Acetyl CoA

NAD+

NADH + H+CO2

Dietary Glucose

Glycogen

2 NADH + H+ × 2.5 ATP ea. 5 5

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.

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])

12Abbreviations: H+, hydrogen; NADH, reduced form of nicotinamide adenine dinucleotide.

Lactate Accumulation and Lactate Threshold (Trained vs Untrained Subjects)

13

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.

VO2 max, %

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

2-carbon acetyl CoA fragment

Oxaloacetate (4 C)

Isocitrate (6 C)

Citrate (6 C)

-ketoglutarate (5 C)

NAD+

NADH + H+

CO2

Succinyl CoA (4 C)

Succinate (4 C)

Fumarate (4 C)

NADH + H+

NAD+

CO2

Inner matrix of mitochrondrion

GDP

GTP

ATP

FAD

FADH2

NAD+

NADH + H+

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

Net result:1 turn of the cycle; 3 NADH, 1 GTP, 1 FADH2, and 2 molecules of CO2 released

The Electron Transport System (ETS)

16

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.

Mitochondrial matrix

Inner membrane

Intermembrane space

ATP Yields: TCA Cycle

TCA cycle (mitochondria) subtotal

17

Acetyl CoA

citrateoxaloacetate

3 NADH + H+

1 FADH2

1 GTP2 CO2

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.

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

18Abbreviations: CoA, coenzyme A; ETS, electron transport system; TCA, tricarboxylic acid.

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

20

Glucose Glycogen

Pyruvate Lactate

Mitochondria

Pyruvate

Acetyl CoA

Cytosol

TCAcycle

PDH

Aerobic

Anaerobic

LDH

NADH + H+

FADH2 ETS

Fatty acid

Activated fatty acid

Activated fatty acid

β-oxidation

ATP

Abbreviations: ATP, adenosine triphosphate; CoA, coenzyme A; ETS, electron transport system; FADH2, reduced form of flavin adenine dinucleotide; H+, hydrogen; LDH, lactate dehydrogenase; NADH, reduced from of nicotinamide adenine dinucleotide; PDH, pyruvate dehydrogenase; TCA, tricarboxylic acid.

Putting It All Together: ATP Yields per Mole Glucosea

Starting from Dietary Glucose Glycogen

Shuttle Malate G-P Malate G-P

Glucose to pyruvate

SLP 2 2 3 3

2 NADH + H+ 4.5 3 4.5 3

Pyruvate to acetyl CoA

2 NADH + H+ 5 5 5 5

Acetyl CoA to CAC/ETS

6 NADH + H+ 15 15 15 15

2 FADH2 3 3 3 3

2 GTP 1.5 1.5 1.5 1.5

ATP TOTALS 31 29.5 32 30.5

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; FADH2, 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.

21

Putting It All Together: ATP Yields With Palmitate Palmitate is a 16-carbon, saturated fatty acid (16:0)

22

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.

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

23Abbreviation: ATP, adenosine triphosphate.

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)

24Abbreviation: CoA, coenzyme A.

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

26

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.

VO2 max, %

300

200

100

025 65 85

cal/

kg/m

in

Plasma glucosePlasma FFAMuscle triglyceridesMuscle glycogen

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

Activity used for Aerobic Long-term anaerobic

Short-term anaerobic

Short-term anaerobic

Maximum duration of use

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

Adapted from McArdle WD et al. Exercise Physiology: Nutrition, Energy, and Human Performance, 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010:371.

27

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

29

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):1070-10769. 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.

Athlete kcal/day kcal/kg/day Study

Male rowers 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

Female gymnasts 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

Reported Energy Intake of Athletes (cont’d)

30

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.

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

Elite figure skaters Ziegler et al2

Men 2,329 (57% carb) 36

Women 1,545 (60% carb)

Female swimmers(taper, collegiate)

2,275 (63% carb) 34 Ousley-Pahnke et al3

Ultra-endurance runner 10,743 (95% carb) 168 Rontoyannis et al4

Bodybuilder Wolinsky5

Offseason 8,159 (no carb) 78

Precompetition 2,624 (4% carb) 29

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)

31Abbreviation: O2, oxygen.

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

32Abbreviations: BMR, basal metabolic rate; METS, metabolic equivalents.

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

33

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.

IOM Physical Activity Levels (PAL) and Coefficients (PA)

34

Plug one of these values into the EERequation

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.

Physical Activity Coefficients (PA Values) for Use in EER EquationsSedentary(PALa 1.0-1.39)

Low Active(PAL 1.4-1.59)

Active(PAL 1.6-1.89)

Very Active(PAL 1.9-2.5)

Typical dailyliving activities (eg, household tasks, walkingto the bus)

Typical daily living activitiesPLUS30-60 minutes of daily moderate activity(eg, walking at 5-7 km/h)

Typical daily living activitiesPLUSat least 60 minutes ofdaily moderate activity

Typical daily living activitiesPLUSat least 60 minutes of daily moderate activityPLUSan additional60 minutes of vigorous activity or 120 minutes of moderate activity

Boys 3-18 y 1.00 1.13 1.26 1.42Girls 3-18 y 1.00 1.16 1.31 1.56

Men 19 y + 1.00 1.11 1.25 1.48Women 19 y + 1.00 1.12 1.27 1.45

IOM Equations for EER

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

Equations to Estimate Energy RequirementInfants and Young ChildrenEstimated Energy Requirement (kcal/day) = Total Energy Expenditure + Energy Deposition0-3 months4-6 months7-12 months13-35 months

EER = (89 × weight [kg] – 100) + 175EER = (89 × weight [kg] – 100) + 56EER = (89 × weight [kg] – 100) + 22EER = (89 × weight [kg] – 100) + 20

Children and Adolescents 3-18 yearsEstimated Energy Requirement (kcal/day) = Total Energy Expenditure + Energy DepositionBoys 3-8 years 9-18 years

EER = (88.5 – (61.9 × age [y] + PAb × [(26.7 × weight [kg]) + (903 × height [m])] + 20EER = (88.5 – (61.9 × age [y] + PA × [(26.7 × weight [kg]) + (903 × height [m])] + 25

Girls 3-8 years 9-18 years

EER = (135.3 – (30.8 × age [y] + PA × [(10.0 × weight [kg]) + (934 × height [m])] + 20EER = (135.3 – (30.8 × age [y] + PA × [(10.0 × weight [kg]) + (934 × height [m])] + 25

Adults 19 years and olderEstimated Energy Requirement (kcal/day) = Total Energy ExpenditureMenWomen

EER = 662 – (9.53 × age [y]) + PA × [(15.91 × weight [kg]) + 539.6 × height [m])]EER = 354 – (6.91 × age [y]) + PA × [(9.36 × weight [kg]) + (726 × height [m])]

PregnancyEstimated Energy Requirement (kcal/day) = Nonpregnant EER + Pregnancy Energy Deposition1st trimester2nd trimester3rd trimester

EER = Nonpregnant EER + 0EER = Nonpregnant EER + 340EER = Nonpregnant EER + 452

LactationEstimated Energy Requirement (kcal/day) = Nonpregnant EER + Milk Energy Output – Weight Loss0-6 months postpartum7-12 months postpartum

EER = Nonpregnant EER + 500 – 170EER = Nonpregnant EER + 400 – 0

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

36

a From IOM PA table.1

b 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.

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/dayUsing 45 kcal/kg:

TER = 60 × 45 kcal/kg = 2,700 kcal/dayUsing 50 kcal/kg:

TER = 60 × 50 kcal/kg = 3,000 kcal/dayUsing 60 kcal/kg:

TER = 60 × 60 kcal/kg = 3,600 kcal/day

37Abbreviations: EER, estimated energy requirement; TER, total energy requirement.

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

Abbreviations: Ach, acetylcholine; ADP, adenosine diphosphate; ATP, adenosine triphosphate; Ca2+, calcium.Reprinted from McArdle WD, et al. Exercise Physiology: Nutrition, Energy, and Human Performance, 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010:370.

ATP Role in Muscle Contraction

40