1. Spotlight on Metabolism and Energy Balance

2. Energy: Fuel for Work Energy source
Chemical energy in carbohydrates, fat, and protein
Transferring food energy to cellular energy
Stage 1: digestion, absorption, and transport
Stage 2: breakdown of molecules
Stage 3: transfer of energy to a form cells can use 2

4. What Is Metabolism? Catabolism
Reactions that break down compounds into small units
Anabolism
Reactions that build complex molecules from smaller ones 4

5. 5

6. What Is Metabolism? Cell is the metabolic processing center Nucleus
Cytoplasm: cytosol + organelles
Mitochondria are the source of many energy pathways 6

8. What Is Metabolism? Who are the key energy players?
ATP is the body’s energy currency
ATP = adenosine triphosphate
Form of energy cell use
NAD and FAD: transport shuttles
Accept high-energy electrons for use in ATP production 8

10. Breakdown and Release of Energy
Pathways initiate breakdown of macronutrients
Anaerobic
Breakdown glucose
Do not require oxygen
Aerobic
Breakdown glucose, fat, and protein
Require oxygen

12. Breakdown and Release of Energy
Extracting energy from carbohydrate
Glycolysis
Pathway splits glucose into two pyruvates
Transfers electrons to NAD
Produces some ATP 12

13. Breakdown and Release of Energy
Extracting energy from carbohydrate
Pyruvate to acetyl CoA
Releases CO2
Transfers electrons to NAD 13

15. Breakdown and Release of Energy
Extracting energy from carbohydrate
Citric acid cycle
Releases CO2
Produces GTP (like ATP)
Transfers electrons to NAD and FAD 15

17. Breakdown and Release of Energy
Extracting energy from carbohydrate
Electron transport chain
Accepts electrons from NAD and FAD
Produces large amounts of ATP
Produces water
End products of glucose catabolism
ATP, H2O, and CO2 17

19. Breakdown and Release of Energy
Extracting energy from fat
Split triglycerides into glycerol and fatty acids
Takes place in mitochondria
Beta-oxidation
Breaks apart fatty acids into acetyl CoA
Transfers electrons to NAD and FAD 19

21. Breakdown and Release of Energy
Extracting energy from fat
Completing fatty acid breakdown
Acetyl CoA from beta-oxidation enters cycle
Citric acid cycle and electron transport chain
Fat burns in a flame of carbohydrate
End products of fat breakdown
ATP, H2O, and CO2 21

22. Breakdown and Release of Energy
Extracting energy from protein
Split protein into amino acids
Split off amino group
Converted to urea for excretion
Carbon skeleton enters breakdown pathways
End products
ATP, H2O, CO2, urea 22

25. Biosynthesis and Storage
Making carbohydrate (glucose)
Gluconeogenesis
Uses pyruvate, lactate, glycerol, and certain amino acids
Storing carbohydrate (glucose  glycogen)
Liver and muscle make glycogen from glucose
Making fat (fatty acids)
Lipogenesis
Uses acetyl CoA from fat, amino acids, and glucose
Storing fat (triglyceride)
Stored in adipose tissue 25

27. Biosynthesis and Storage
Making ketone bodies (ketogenesis)
Made from acetyl CoA
When inadequate glucose in cells
Making protein (amino acids)
Amino acid pool supplied from
Diet, protein breakdown, and cell synthesis
Biosynthesis
Different pathways used to build amino acids from carbon skeletons 27

29. Special States Feasting
Excess energy intake from carbohydrate, fat, protein
Promotes storage
Fat  adipose tissue
Amino acids  protein synthesis
Carbohydrate  adipose tissue 29

30. Special States Fasting Inadequate energy intake Promotes breakdown
Prolonged fasting
Protects body protein as long as possible 30

31. Special States Fasting
Survival priorities and potential energy sources
Preserve glucose-dependent tissue
RBC, brain cells, central nervous system
Maintain muscle mass

32. Special States Fasting The prolonged fast: In the beginning
Blood glucose drops, liver breaks down glycogen to glucose
Gluconeogenesis
Fat and protein are primary fuel

33. Special States Fasting The early weeks
Several energy-conservation strategies
Several weeks of fasting
Rely on stored body fat
The end is near
Muscle atrophy and emaciation
Sacrificed muscle tissue in attempt to preserve brain tissue

34. Energy Balance Energy intake vs. energy output Energy equilibrium
Intake = output
Maintain weight 34

35. Energy Balance Positive energy balance Intake > output Gain weight
Negative energy balance
Intake < output
Lose weight 35

36. Energy In Regulation of intake Internal cues Hunger Prompts eating
Satiation
Signals to stop eating
Satiety
Tells when you are ready to eat again 36

38. Energy In Regulation of intake External cues Appetite
Psychological desire to eat
Influenced by the eating environment 38

39. Energy In Control by committee What stimulates our cues?
Internal, physiological response
Eating environment 39

40. Energy In Internal factors Gastrointestinal sensations
Sense of fullness
Neurological and hormonal factors
Neuropeptide Y
Ghrelin
Leptin 40

41. Energy In External factors Diet composition
Energy density, balance of energy sources, and form
Macronutrients
Sensory properties
Taste 41

42. Energy In External factors Portion size Super-size culture
Environment and social factors
Hypothalamus
Emotional factors 42

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44. Energy Out: Fuel Uses Total energy expenditure
Major components of energy expenditure
Energy expenditure at rest (basal energy expenditure)
Energy for basic body functions
Affected by body size, composition, age, and gender 44

45. Energy Out: Fuel Uses Major components of energy expenditure
Physical activity
Highly variable
Affected by body size, fitness level, type of activity
Thermic effect of food (TEF)
Energy to digest, absorb, metabolize food 45

47. Energy Out: Fuel Uses Estimating total energy expenditure
Resting energy expenditure (REE)
1.0 kcal/kg/hr for males
0.9 kcal/kg/hr for females
Physical activity
Add a % of REE (see Table 8.2)
Thermic effect of food
6% to 10% of (REE + physical activity) 47

48. Estimating Energy Expenditure
Estimated Energy Requirement (EER)
Equations for males and females
Factors for age, weight, height, and physical activity
Predicts total energy expenditure (TEE) 48

49. Body Composition Body composition Fat and lean muscle mass
Assessing body weight
Body mass index (BMI)
Weight (kg) × height2 (m)
BMI ≤ 18.5 kg/m2 = underweight
BMI 18.5 to ≥ 25 kg/m2 = normal weight
BMI 25 to ≤ 30kg/m2 = overweight
BMI ≥ 30 kg/m2 = obese 49

50. Body Composition Assessing body fatness DXA Underwater weighing BodPod
Skinfold measurements
Bioelectrical impedance 50

51. Body Composition Body fat distribution Gynoid obesity (“pear”)
Excess fat in hips and thighs
Android obesity (“apple”)
Excess fat around abdomen
Waist circumference 51