Energy

1
7. Energy and Food chapter 8
2
Energy the ability to do work
A calorie is the amount of heat (or energy)
needed to raise the temperature of one gram of
water by one degree Celsius. A kilocalorie
(kcal) is 1000 calories. A joule is 0.24
calories.
Almost all of the chemical energy contained in
any substance is stored in its chemical bonds.
3
calorie vs kilocalorie
4
Bond Energy

• The E required to break a chemical bond or
• The E released when the bond is formed
• C-H 100 kcal/mole C-C 90kcal /mole
• O-H 110 kcal/mole CO 170 kcal/mole
• OO 118 kcal/mole

5
An exothermic reaction is a reaction that
releases heat as it proceeds . CH4
2O2 CO2 2H2O energy
exo
endo
An endothermic reaction is a reaction that
absorbs heat as it proceeds .
6
Why is this reaction exothermic?

• E required to break the bonds of reactants is 4 x
  C-H bond E 2 x (OO) bond energy 4 (100)
  (2 x118) 636 kcal
• E liberated when bonds of products are formed 2
  x (CO) bond Energy 4 x (O-H) bond E ie
  (2x170) 4 (110) 780 kcal
• Thus Energy is released in this reaction
  780-636 144 kcal/ mole of methane burned

7
FOOD FUEL FOR THE HUMAN ENGINE
The Energy Equation Energy In Energy Out
Energy Stored
Metabolism is the combination of all chemical
reactions that take place in any living organisms.
1 Kilocalorie 1 nutritional Calorie (Cal)
8
ENERGY IN The Macronutrients
The macronutrients of our food are the three
major groups that make up the great bulk of our
food supply, the chemicals that serve as the only
source of energy for the human machine .
9
Through the elegant, intertwined complex of
chemical reactions that constitute human
metabolism, the chemical energy of these
compounds becomes transformed into the human
energy of our lives .
The Macronutrients fats and oils
carbohydrates protein
10
Energy from Macronutrients

• From fat 9 Calories per gram
• From protein 4 Calories per gram
• From carbohydrate 4 Calories per gram

11
Why do we get more calories from fat than from
carbs or protein?

• Fats contain long hydrocarbon chains in the fatty
  acid part of the molecule
• More C-H bonds to be oxidized to Water and CO2.
• Recall relatively high bond Energy in CO and O-H
  vs. C-C and C-H bonds (methane combustion ).

12
Calories for Healthy Eating

• Recommended levels from macronutrients
• From carbohydrates (55) 10 from simple sugars
  (sucrose, glucose, fructose) 45 from complex
  carbohydrates (starch)
• From fat (30) maximum 10 from saturated fat,
  best from unsaturated
• From Protein (15)

13
Some would disagree

• Atkins Diet advocated as few calories as
  possible from carbohydrates
• Theory (1972 book) was that sugars and
  carbohydrates increase insulin levels and
  facilitate fat storage
• Depriving the body of carbohydrates facilitates
  fat burning and hence weight loss

14
Problems with the Atkins diet

• Too much saturated fat - coronary disease
• Too little fibre, hence poor waste product
  elimination and risk of kidney disease and colon
  cancer
• Conclusion Not a healthy alternative
• Expensive Permitted foods were Atkins Diet
  products

15
Atkins Diet products
16
North American Problems

• Too much simple sugar
• Too much saturated fat
• Too many calories!!
• Not enough physical activity
• Obesity is a major health issue

17
Micronutrients

• Food components such as Vitamins and Minerals,
  which are required in relatively small amounts
  for good health
• Not significant sources of calories

18
What is Junk Food?

• Food that supplies a large number of calories but
  few Vitamins or Minerals (Micronutrients)
• Empty Calories ie. highly refined sugar
  (Sucrose) provides calories but no micronutrients

19
EmptyCalories from soft drinks

• Classic Coke 42 grams of sugar per 341 mL can x4
  Cal/gr 168 Calories
• Diet Coke no sugar, artificial sweeteners
  (aspartame and potassium acesulfame) 0 Calories
  (on can)
• Carbonated water, caramel flavor, caffeine,
  phosphoric acid, citric acid, sodium benzoate,
  0.1 gr of protein, so not quite 0 Cal.

20
Enzymes in Digestion

• Enzymes (bio-catalysts) help to break down
  complex substances into simpler ones which can be
  absorbed
• Need optimal pH-ie pepsin in the stomach works
  best at pH near 2
• Suffix ase denotes an enzyme

21
Carbohydrase enzymes

• Amylase in saliva, breaks starch and complex
  carbohydrates into maltose
• Maltase then breaks the maltose into glucose
• Sucrase, lactase act on sucrose and lactose
  breaking them down into simpler sugars such as
  glucose and fructose

22
Protease enzymes

• Pepsins-secreted in stomach and pancreas to help
  proteins break down into peptides and eventually
  into amino acids

23
Lipases

• Secreted in pancreas and walls of the small
  intestine
• Digest lipids (fats) and breaks them up into
  fatty acids and glycerol

24
Digestion
25
ENERGY OUT
Exercise Specific Dynamic Action Basal
Metabolism
26
Specific dynamic action, SDA, the energy
consumed in digesting and metabolizing food and
converting its energy for use in exercise and
basal metabolism. It is the price we pay, in
energy, for extracting energy from food .
(10 of
the energy obtained from food) ie. consume
2500Cal and use 250Cal for SDA
27
We can sense SDA in operation as we grow warmer
and find our heart beating a bit faster after a
meal. The warmth and higher pulse are both signs
that our body is working at digesting the food
and using up energy through SDA. Drowsiness
after a large meal comes from the diversion of
blood from the brain to the digestive system. The
body is working hard to process all the fuel
thats just been brought in and - first things
first - digestion takes momentary precedence over
mental alertness.
28
After a great dinner!
29
Basal metabolism accounts for all the work that
goes on inside our bodies just to keep us alive.
It is the energy expended as our heart pumps, as
our lungs expand and contract, and as the liver,
kidneys and other major organs work to maintain
life .
30
In a healthy adult the energy spent through
Basal Metabolism amounts to approximately
1 Calorie / hour / kg of body weight
Basal metabolism increases with any bodily
stress, desirable (eg. pregnancy or lactation) or
not (eg. illness). Measured at rest, but awake,
after a 12 hour fast
31
Calorie needs for inactive male

• For 70 kg (154lb) man need 24 x 70 1680 Cal
  per day for basal metabolism
• But also need additional amount for SDA which is
  about 10 more. Thus 1900 Cal/day total

32
Resting metabolism represents the combination of
basal metabolism and SDA.
33
(No Transcript)
34
Energy Availability Storage

• Instant blood sugar (Glucose) lasts ca. 30
  minutes
• Short term Liver and muscles store glycogen
  (about 2500 Calories) max 6-8 hours.
• Long term fat is stored in adipose tissue-can
  last up to 35 days

35
Hitting the Wall

• Marathon runners use 15Cal/minute
• After 2.5 hours, use 150x 152250 Cal
• Glycogen tank is empty!!
• Need to consume short term E glucose etc.
• Fat metabolism is slow and thus of no use as a
  short term E source

36
(No Transcript)
37
Water content of adipose tissue

• Why only 7.7 Cal/gram stored in adipose tissue if
  fat provides 9 Cal/gram?
• A 15 of adipose tissue is water
• Thus 9- (.15x9) 9- 1.35 7.65 Cal/gram

38
(No Transcript)
39
The evolution of man

• Sedentary lifestyle needs fewer calories

40
(No Transcript)
41
Daily Energy Needs According to Physical Activity
Activity Level
Factor
Very light Men Women Light
Men Women Moderate Men Women Heavy
Men Women
To estimate your energy needs , multiply your
estimated BMR (10x your weight in lbs.) by the
factor listed in the table that best represents
your general level of daily activity. Very Light
mostly sitting and standing activities
Light mostly walking activities Moderate
cycling, tennis, dancing Heavy heavy manual
digging, climbing, basketball, soccer
1.3
1.3
1.6
1.5
1.7
1.6
2.1
1.9
42
Typical 175 pounder

• Caloric requirement is 10x 175 x1.3 if inactive,
  ie 2275 Calories per day.
• If you play for the Ottawa Senators, 175 x 10 x
  2.1 3675 Calories per day
• Females a bit lower ca 1900 Cal/day
• Q Do women have more efficient metabolisms? A
  yes! Women have less muscle and more fat (on the
  average).

43
How many soft drinks per day?

• Recall max. 10 of Cal. from simple sugars, so
  10 of 2275 227.5 Cal/
• Recall one can of regular Coke contains over 160
  Cal
• So, the answer is..1 .

44
Calories from Alcohol

• 7 Calories per gram
• Thus in a 341mL can of normal beer (5 ),
  assuming its density is 1 gram per mL
• Calories .05 x 341 x 7 119.35
• A glass of wine or a shot (1.5 oz of liquor) have
  about the same caloric content
• No nutrients, depresses CNS and is toxic to liver

45
Recommended levels of alcohol

• Max. 2 drinks per day (male adult)
• Max. 1 per day (adult female)
• 0 per day if pregnant or lactating!
• 0 per day if on certain medications
• Moderation is KEY!!

46
Approximate Rates of Energy Expenditure for a
70kg (154lb) Person
Calories Expended
Level
Examples
Per Minute
Per Hour
Very light Sitting, reading, watching TV,
writing, driving Light Slow
walking, washing, shop- ping,light sports
such as golf Moderate Fast walking, heavy
gardening, moderate sports such as
bicycling, tennis, dancing Heavy Vigorous
work, sports such as swimming, running,
basketball and football
1.0-2.5
60-150
2.5-5.0
150-300
5.0-7.5
300-450
7.5-12.0
450-720
47
Energy used in a Variety of Activities
Activity
Energy (Cal/min)
Bicycling, 15 mph Bicycling, 5mph Chopping wood
Driving an automobile Eating Gardening,
weeding Listening to lecture Pick and shovel
work Running 5 mph Skiing, cross country
Swimming, pleasure Tennis, (recreational/competi
tive) Walking 3-5 mph Walking up stairs
12 5 7.5 2.8 1.5 5.6 1.7 6.7 10 9-17 6 7/11 5.6 10
-18
48
DEMO Energy from snack foods

• Potato is mostly carbohydrate-ie 4 Cal/gram
• But , if it is deep fried in fat, add 9 Cal per
  gram of fat
• Burning potato chip fat burns off
• Black residue is just Carbon
• Salt NaCl adds yellow colour to flame