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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
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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.
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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
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Supplementary Slide on ATP and muscle
contraction
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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.
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