Energy Balance

“Aside from the limits imposed by heredity and the physical improvements associated with training, no factor plays a bigger role in exercise performance than does nutrition.”

Dr. David Costill, 1988

Energy Balance

Hypothetical daily energy needs of an Ironman triathlete in training.

Activity METS Duration (h)

Energy Expenditure (kcal)

Sleep 0.9 8.0 540

Office work 1.5 8.0 900

Running (7.5 mph)* 13.5 0.8* 810

Swimming (2 mph)* 8.0 0.5* 318

Bicycling (18.6 mph)* 12.0 1.7* 1,530

Home activities (e.g. cooking, washing dishes, etc.)

2.5 3.0 563

Miscellaneous activities (reading newspaper, talking on phone, etc.)

1.3 2.0 195

      4,856

*Based on data from O’Toole, 1989. Energy expenditure calculated as: (METS 75 kg body weight hours of activity = kcal)

Daily Energy Intakes of Elite AthletesSport Energy Intake (kcal/d) Reference

Tour de France 5,972 Van Erp-Baart, 1989

Triathlon 4,778 Van Erp-Baart, 1989

Cycling 4,300 Van Erp-Baart, 1989

Swimming 4,018 Grandjean, 1989

Football (U.S.) 3,826 Grandjean, 1989

Soccer 3,583 Van Erp-Baart, 1989

Body Building 3,344 Van Erp-Baart, 1989

Running 3,105 Van Erp-Baart, 1989

U.S. Males (19-34) 2,667 Grandjean, 1989

Map of the Trek

Torry Larsen Rune Gjeldnes

WR 2,928 km Unsupported Ski Trek March - June, 1996

WR 2,928 km Ski Trek

Details

• 2,928 km (1,815 miles) in 83 days• 9 hrs/d of trekking (~22 miles/d)• Each pulling 150 kg (330 lb sled)• Average energy intake was 6,000 kcal/d• Average weight loss was only 5.3 kg (~12 lbs) and

4% reduction in body fat (DEXA)• Average weight loss of Army Rangers during 64

days of training is 10 – 20 kg (22 – 44 lbs)!

Macronutrients

60 -70% of kcal350-600g/d5-10g/kg/d

CHOPRO

FAT

15-25% of kcal

15% of kcal1.2-1.8g/kg/d

Macronutrient Composition and Performance:Overview

Dietary Protein

0.3 0.5 0.7 0.9 1.1 1.3 1.5 Protein Intake (g/kg/d)

80

60

40

20

0

-20

-40

-60

-80

Nitr

oge

n B

ala

nce

(m

g/k

g/d

)

RDA

Meredith et al., 1989

Mean = .94g/kg/d

300

250

200

150

100

50

Wh

ole

Bo

dy

Pro

tein

Syn

thes

is (

mg/

kg/h

r)

0.9 1.4 2.4 Protein Intake (g/kg/d)

Sedentary

Strength Athletes

Tarnopolsky et al., 1992

* *

Current Protein Intake Recommendations

Adult RDA (1989) 0.8g/kg/d

ADA/CDA Recommendations for Active People(1993)

1.0-1.5g/kg/d

Foods, Nutrition, and Sports PerformanceInternational Scientific Consensus (1992) Strength Athletes Endurance Athletes

1.2-1.8g/kg/d1.2-1.4g/kg/d

Current U.S. Intake Data, NHANES II (1991) ~1.6g/kg/d

Nationwide Survey on Nutritional Habits of EliteAthletes (van Erp-Baart et al., 1989) Strength Athletes Endurance Athletes

1.4-2.5g/kg/d1.3-3.0g/kg/d

Protein and Amino Acid Contents of Common Foods and Popular

Supplements

Food or Supplement Amount Equal to 24g Protein Price/serving

Skim Milk 3 cups (24 fl oz) $0.55

Liquid Gainer’s Fuel 1 bottle (also ~ 24 fl oz) $2.79

Dry milk powder 1 cup $0.17

Gainer’s Fuel powder 3 scoops $0.86

Amount Equal to 7g AA’s

Chicken breast 1 oz $0.10

Amino Fuel AA’s 13 tablets $1.62

Dietary Carbohydrate

Why Are Carbohydrates So Important?

Carbohydrates are the primary muscular fuel source for intense exercise

0

10

20

30

40

50

60

Rest 20% 40% 60% 80% 100%

AEROBIC POWER

FA

T (

%)

40

50

60

70

80

90

100

CH

O (%

)FAT

CHO

Adapted from: Brooks and Mercier, 1994The “Crossover Concept”

0

50

100

150

200

250

300

350

25 65 85

% VO2max

kca

l/k

g/m

inMuscle Glycogen

Muscle Triglycerides

Plasma FFA

Plasma Glucose

Adapted from: Romijn et al., 1993

Why Are Carbohydrates So Important?

Carbohydrates are the primary muscular fuel source for intense exercise

Carbohydrate body stores are limited; when depleted, athletes cannot exercise intensely and experience fatigue

0

0.5

1

1.5

0 15 30 45 60

Work Time (min)

Mus

cle

G ly

coge

n(g

/100

g w

et m

uscl

e)

Adapted from: Bergstrom and Hultman, 1967

0

10

20

30

40

50

60

70

80

90

0 10 20 30 40 50 60 70 80 90 100 110 120

Time (min)

Mus

cle

Gly

coge

n (m

mol

/kg

ww

)

150% VO2max

120% VO2max83% VO2max 64% VO2max

Adapted from: Gollnick, 1974

Adapted from: Bergstrom et al., 1967

0

1

2

3

4

5

0 50 100 150 200 250 300

Time to Exhaustion (m in) at 75% VO2max

In it

ial M

uscl

e G

lyco

gen

(g/1

00g

m u

scle

)

r = 0.92

Low CHO Diet Normal Diet High CHO Diet

Why Are Carbohydrates So Important?

Carbohydrates are the primary muscular fuel source for intense exercise

Carbohydrate body stores are limited; when depleted, athletes cannot exercise intensely and experience fatigue

Athletes who train regularly and intensely require more dietary carbohydrates to replenish what is used

0

20

40

60

80

100

120

140

0 2 12 24 26 36 48 50 60 72

Time (hrs)

Mus

cle

Gly

coge

n (m

mol

/kg

wet

wt.

)High CHO Diet

(~575 g/d)

Low CHO Diet(~250 g/d)

Training Bouts (2 hrs)

Adapted from: Costill, 1985

Are athletes eating enough carbohydrates?

Recommendations for Training

Absolute CHO intakes should approach 350-600g/d or 5-10g/kg/d

The % of calories coming from CHO is not as important as long as absolute needs are met

16.3 16.6 16.5 15.8

52.745.451.844.5

3237.230.937.6

0

20

40

60

80

100

GeneralPopulation (M)

MarathonRunners (M)

GeneralPopulation (F)

MarathonRunners (F)

Per

cent

of

Tot

al E

nerg

y In

tak

eCHO FAT PRO

Adapted from: Nieman et al., 1989

Making Sense of CHO Recommendations

Body Wt. (kg) Kcal

CHO (%) CHO (g/d) CHO (g/kg)

70 4200 45 473 6.8

70 3700 60 560 8.0

70 2000 70 350 5.0

0

200

400

600

800

1000

1200

80% CHO Diet 43% CHO Diet

Tot

al C

HO

(g/

d)

12.1g/kg 6.5g/kg

4,675 kcal /d

4,675 kcal /d

Data from: Lamb et al., 1990

Typical CHO Intakes of Endurance Athletes

Subjects n CHO (g/d) CHO (%) Study

Distance Runners 10 396 49 Grandjean(1989)

Marathon Runners 19 487 52 Burke et al.,1991

Distance Runners 50 417 53 Williams,1992

Triathletes 25 627 60 Burke et al.,1991

Why Are Carbohydrates So Important?

Carbohydrates are the primary muscular fuel source for intense exercise

Carbohydrate body stores are limited; when depleted, athletes cannot exercise intensely and experience fatigue

Athletes who train regularly and intensely require more dietary carbohydrates to replenish what is used

Carbohydrates consumed before, during, and after exercise maximize performance

Effect of CHO Feedings 2-4 hrs Before Exercise

Studies Exercise (+) Effect No Effect ( - ) Effect

7 (1987 –1999)

Cycling / Running at52 – 100% VO2max

4 2 1

Effect of CHO Feedings 30-60 min Before Exercise

Studies Exercise (+) Effect No Effect ( - ) Effect

11 (1979 –1994)

Cycling / Running at60 – 80% VO2max

3 4 3

Glycemic Index of Common Foods

High Moderate Low

Potato Banana Raisins Glucose Sucrose Bagel

Spaghetti Oatmeal Orange Grapes Potato Chips Sponge Cake

Apples Lentils Baked Beans Fructose Milk Tomato Soup

During & Early After Exercise

Before and Late After Exercise

Before and Late After Exercise

Effect of CHO Feedings During Exercise

Studies Exercise (+) Effect No Effect ( - ) Effect

19 (1984 –1998)

Cycling / Running at50 – 90% VO2max

17 1 1

Sports Drinks

Sports Drink CHO Type Concentration Calories (8 fl.oz.)

All Sport Sucrose,Fructose

8% 70

Exceed Glucose poly-mer, Fructose

7% 70

Gatorade Sucrose,Glucose

6% 50

PowerAde Fructose,Sucrose

8% 67

3

3.5

4

4.5

5

5.5

6

6.5

7

0 30 60 90 120 150 180 200

Time (min)

Pla

sma

Glu

cose

(m

mol

/L)

8% CHO

Placebo*

** * *

FATIGUE

Adapted from: McConell et al., 1999

3.4

3.6

3.8

4

4.2

5 10 15 20 25 30

Distance (km)

Ru

nnin

g S

pee

d (

m/s

ec)

CHO Trial (5% CHO drink)

Control Trial (water only)

Adapted from: Tsintzas et al., 1993

0

50

100

150

200

250

300

Placebo Pre-CHO Ex-CHO Both

Tim

e to

Exh

aust

ion

(min

) 18%

32%44%

Adapted from: Wright et al., 1991

Dorando Pietri, 1908 Olympic Marathon

Carbohydrates and Performance

Carbohydrates in the post-exercise period: Glycogen Resynthesis

82

91

86

70

40

50

60

70

80

90

100

Day 1 Day 2

Run

Tim

e (m

in)

at 7

0% V

O2m

axHigh CHO (9g/kg) Moderate CHO (6g/kg)

*

Adapted from: Fallowfield et al., 1993

Practical Recommendations

Time Period Carbohydrate Comments

Daily Training 5-10g/kg/d Dependent on intensity andduration of training

CHO Loading 5g/kg 3d, then>8g/kg 3d

For events > 90 min; depletingexercise then taper

Pre-Exercise 1-2g/kg 1-2 hr4-5g/kg 3-4 hr

Consume familiar foods

During Exercise .5-1g/kg/hr For events > 90 min; up to10% CHO solution

After Exercise .75-1.5g/kg/hr Begin as soon as possible forup to 4 hrs

Nutrition and Athletic Performance:Summary

• Number one nutritional priority is maintaining energy balance

• Athlete protein needs are higher than the RDA, but athletes* already consume even more than the upper scientific recommendations

• Carbohydrate needs are best expressed on a g/kg/d basis (or in absolute terms: 350-600g/d)

• Carbohydrates improve athletic performance for endurance exercise (> 90 continuous minutes)