Energy Value of Food and Physical Activity

1
Energy Value of Food and Physical Activity

• Chapter 13

2
Digestive Efficiency

• Carbohydrate 97
• Lipids 95
• Proteins 97 78 (depending on source Average
  92)

3
Human Energy Efficiency

• 40 at best
• Compared to 30 for gasoline / steam engine
• Additional energy liberated as heat
• Provides body heat
• Must be dealt with when large amounts of heat are
  produced during exercise

4
Calorie (kcal)

• Energy needed to heat 1 kg water 1 Co
• Big Mac and Fries 783 kcal
• Energy to raise temperature of 196 gallons of
  water 1 degree centigrade!
• Energy is measured in a bomb calorimeter

5
A CALORIE IS A CALORIE

• ALL CALORIES ARE EQUAL!

6
Oxygen and Calories

• Caloric value of 1 liter of oxygen
• 4.5 kcal for protein
• 4.7 kcal for lipid
• 5.0 kcal for carbohydrate
• We will round all to 5 kcal / liter of O2
• By measuring VO2 we can determine caloric
  expenditure (spirometry)!

7
Energy Expenditure

• Basal Metabolic Rate (BMR) - 60-75
• Resting metabolism
• Thermogenic influence of food digestion 10
• Exercise and recovery 15-30

8
Metabolism
9
BMR

• Effected by
• Body Size
• Measured as BSA
• 38 kcal/m2 men
• 36 kcal/m2 women
• Lean body mass
• Gender
• GENETICS
• Generally ranges between 900 1900 kcal

10
Calculating BMR (example)

• What is the BMR of a 6 1 male weighing 195 lbs.
  ?
• First determine BSA using nomogram, then multiply
  by BMR constant 24 hours
• 38 kcal/m2/hr BSA 24 hr/day

11
BMR

• BSA 2.1 m2
• BMR 38 kcal / m2 / hour X 2.1 m2 X 24 hours
• BMR 1,915 kcals / day

12
Dietary Thermogenesis

• Food intake stimulates metabolism
• Digestion
• Absorption
• Assembly of nutrients (ie proteins)
• Highest 1 hour post eating
• 10-25 of energy of food eaten
• Exercise augments this response (2X)

13
Exercise and Energy Expenditure

• Affected by
• Body mass
• Intensity
• Duration
• Training

14
Energy cost of Exercise

• Same 61, 195 lb. man, running at VO2 of 40 mL
  O2/kg/min for 30 min.
• What is the total energy expended?
• What is the energy cost for exercise?
• Answer
• First determine O2 consumed
• .04 L O2 X 88.6 kg X 30 min
• 106.32 L O2 consumed

15
Energy cost of Exercise

• Now determine the energy required to utilize
  106.32 L O2
• 106.32 L O2 X 5 kcal/liter 531.6 kcal
• Total kcals 532 kcal

16
Energy cost of Exercise

• To determine energy cost of exercise, you must
  subtract kcals burned for BMR
• 532 kcal BMR30min.
• BMR30min. 38 kcal X 2.1 m2 X .5 hours
• BMR30min. 40 kcal
• Energy cost of exercise 532 40 kcal
• 492 kcal

17
Quantifying work in METs

• MET Metabolic Equivalent
• Multiple of BMR
• IE exercising at 3 METs utilizes three times the
  rate of energy at rest for that individual.
• In our example
• 492 kcalexercise / 40 kcalBMR 12.3 METs