fats

1. Fats
Chapter 6
Nutrition for Sport and Exercise
Dunford & Doyle

2. Learning Objectives
1. Classify fats according to their chemical
composition.
2. Distinguish between saturated and unsaturated,
monounsaturated and polyunsaturated, cis and
trans, and omega-3 and omega-6 fatty acids.
3. Describe the digestion, absorption, transportation,
and storage of fat.
4. Explain the metabolism of fat, including
mobilization, transportation, uptake, activation,
translocation, and oxidation.
5. Explain ketosis and the effect it may have on
training

3. Learning Objectives, con’t
6. Describe how the body uses fat to fuel
exercise.
7. State fat recommendations for athletes and
calculate the amount of fat needed daily.
8. Identify sources of dietary fat.
9. Assess an athlete’s dietary fat intake.
10. Evaluate fat-related dietary supplements.

4. Introduction to Fats
 The word fat has many different meanings
 Important source of energy at rest and during
low-intensity exercise
 Most concentrated source of energy (9 kcal/g)
 Fats are distinguished by their chemistry
 Certain fats in food and in the blood are
associated with cardiovascular disease

5. It is important to know the amounts and types of
dietary fats found in foods.

6. Fatty Acids
 Chains of carbon and hydrogen
 Chain length varies from 4 to 24 carbons (even
numbers only)
 Double bonds are a distinguishing factor
 Double bond formation is a distinguishing factor

7. Oleic Acid
Figure 6.1

8. Saturated, Monounsaturated, and
Polyunsaturated Fatty Acids
Figure 6.2

9. Vegetable oils are excellent sources of
monounsaturated and polyunsaturated fatty acids.

10. Fatty Acid cis and trans Formations
Figure 6.3

11. Omega-3, -6, and -9 Fatty Acids
Figure 6.4

12. Structure of Triglycerides
Figure 6.5

13. Fatty Acid Distribution in Selected Foods
Figure 6.6

14. Sterols and Phospholipids
 Sterols have a ring structure
• Cholesterol
• Vitamin D
• Sex hormones
 Cholesterol
• Only found in animal foods
• Also manufactured in the body
 Phospholipids
• Similar in structure to triglycerides
• Contain phosphate
• Component of cell membranes

15. Structure of Sterols
Figure 6.7

16. Cholesterol is only found in animal foods such as
milk and milk products in which the fat has not been
removed.

17. Fats and Performance and Health
 From a performance perspective
• Fat provides energy at rest and during low-
intensity exercise
• Released from storage in adipose tissue
• Released from storage in muscle
• The original source from food (e.g. saturated vs.
unsaturated) is not important

18. Fats and Performance and Health
 From a health perspective
• Intake of certain fats may reduce heart disease
risk
• Omega-3 fatty acids
• Intake of certain fats may increase heart disease
risk
• Saturated fatty acids
• Dietary cholesterol (in some people)
 Athletes must balance both perspectives

19. Digestion of Fats
 Small intestine
• Pancreatic lipase
• Di- and monoglycerides
 Gastric emptying rate
 Satiety

20. Transportation of Fats
 Fatty acids are released into blood via the portal
vein
 Blood fatty acid concentration is increased for
several hours
 Cellular triglyceride absorption
• Adipose and muscle cells are important storage
sites
• Lipoprotein lipase (LPL) stimulates the release of
fatty acids from the triglycerides

21. Fat Storage
 Lipoprotein lipase activity is stimulated by insulin
 Fatty acids are re-assembled in adipose and
muscle cells
• Subcutaneous and visceral fat
• Slow-twitch skeletal muscle, heart muscle
 Advantages
• 9 kcal/g (twice that of CHO or protein)

22. Ketosis
 Ketone bodies
• Acetoacetate
• Beta-hydroxybutyrate
• Acetone
 Normal metabolic pathway
 ~2 to 6% of body’s energy needs after overnight fast
 Pathway is sometimes emphasized
• Starvation state
• Low CHO intake
• Impaired CHO metabolism (diabetes)
• Dangerous, can result in ketoacidosis

23. Ketosis, con’t
 Low CHO intake/ starvation
• Ketones are source of energy for brain
• Muscle glycogen depleted
• Loss of some skeletal muscle
• Weight (fat) loss
 Not likely to be beneficial for athletic
performance

24. Fats as an Energy Source During Exercise
 Use of fat during exercise
• Advantages
• Abundant in food supply
• Energy dense
• Substantial storage in adipose tissue
• Produces large amount of ATP
• Disadvantages
• Takes time to transport and metabolize
• Requires oxygen

25. Relative and Absolute Fat Oxidation
 Relative
• % energy derived from CHO or fat
 Absolute
• Total amount of energy expended

26. Energy Expenditure and Fuel Utilization

27. Exercise Intensity and Relative Fat and
Carbohydrate Oxidation
Figure 6.10

28. Exercise Intensity and Absolute Fat and
Carbohydrate Oxidation
Figure 6.11

29. Exercise Duration and Percentage of Fat and
Carbohydrate Used
Figure 6.12

30. Do You Have to Burn Fat to Lose Fat?
 Low-intensity exercise (“fat-burning zone”)
• RER is lower than during high-intensity exercise
• % energy derived from fat is high
• Total amount of energy expended is lower
 Not necessary to burn fat during exercise to lose
body fat
 Total energy expended is more important than %
expended from fat

31. Effects of Training on Fat Usage
 General adaptations
• Fatty acids are more easily mobilized from
adipocytes
• Uptake of fatty acids into muscle cells is
enhanced
• Number and size of mitochondria are increased

32. High-fat Diets - Fat loading
 Endurance performance not likely to improve
 Intensity of exercise would be too low to be
competitive

33. Effect of Caffeine on Fat Usage
 Dose: 5 to 6 mg/kg body weight
 Does not increase fat mobilization
 Central nervous system stimulant
• Increases sense of awareness
• Decreases perceived effort
 May be banned substance
 Normal use not likely to exceed threshold
 Caffeine is addictive and has side effects

34. Carnitine Dietary Supplements
 Found in food and synthesized from lysine
 Deficiencies are rare
 Supplement dose: 2 to 4 g/day
 Supplements seem to be safe at such dosages
 Little evidence of effectiveness

35. Medium-chain triglyceride Supplements
 Not effective for improving endurance
performance
 May impair performance in some cases

36. Fat Recommendations for Athletes
 General considerations
• Total energy (kcal) need
• Macronutrient balance
• Higher CHO/protein intake typically means lower
fat intake
• Severe restriction of fat intake not recommended
• Often expressed as a % of total energy intake
• 20 to 35% total caloric intake
• May be expressed on g/kg body weight basis
• ~1.0 g/kg daily
• May need to be as high as 3.0 g/kg
(ultraendurance athletes)

37. Fat Recommendations for Athletes
 Adjusting fat intake to achieve energy deficits
• Reducing body fat may result in improved
performance
• Fat intake is typically reduced since reductions to
CHO or protein intakes may be detrimental to
performance
• Athletes may consume a short-term, low fat diet
to achieve body composition goals

38. Fat Recommendations for Athletes
 Effects of an inadequate fat intake on training,
performance, and health
• Inadequate replenishment of intramuscular fat
stores
• Inability to manufacture sex-related hormones
• Decline in high-density lipoprotein cholesterol
(HDL-C)
• Inadequate fat-soluble vitamin intakes

39.  Amounts and types of fats in food
• Predominantly monounsaturated
• Olive, canola, and peanut oils
• Some safflower oils
• Avocado
• Nuts
Translating Fat Recommendations to
Food Choices

40.  Amounts and types of fats in food
• Predominantly polyunsaturated
• Corn, soy, and flaxseed oils
• Some safflower oils
• Liquid and soft (tub) margarines
• Mayonnaise and some salad dressings
• Sunflower, pumpkin, and flax seeds
Translating Fat Recommendations to
Food Choices

41.  Amounts and types of fats in food
• Predominately or some saturated
• Bacon grease and lard
• Hard (stick) margarine
• Butter, cream
• Coconut oil
Translating Fat Recommendations to
Food Choices

42.  Fat substitutes
• Often made from CHO sources
• Such products may not have fewer kcal than
original product
• Olestra (Olean®) is not absorbed
• Not a weight loss panacea
Translating Fat Recommendations to
Food Choices

43. The fat intake of a bodybuilder will vary depending on the
training cycle.

50. The Americanization of traditional ethnic meals often
results in the addition of fat.

52. Grilling and steaming are preparation methods that
do not require additional fat.

53. Beverages may be a source of fat.

54. Summary Concepts
 Precise terminology is important to prevent
confusion when discussing fat-related issues.
 Fats must be considered in several contexts,
including the effect they may have on
performance and health.
 Fats are an important source of energy at rest
and during low-intensity exercise.
 Fat absorption, digestion, transportation, and
metabolism are slow and complicated when
compared to carbohydrate.

55. Summary Concepts, con’t
 For athletes in training, the need to balance
carbohydrate, protein, and fat intakes results in
a diet that is typically lower in fat than that of the
general population.
 Fats contain more kilocalories per gram than
carbohydrates, protein, and alcohol and are
easily stored in adipose tissue as a future
energy source.
 Fats in foods contribute to their good taste and it
is easy to consume excess fats and kilocalories.