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week4.pptxSpotlight on Metabolism and Energy Balance
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
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What Is Metabolism?
Catabolism
Reactions that break down compounds into small units
Anabolism
Reactions that build complex molecules from smaller ones
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What Is Metabolism?
Cell is the metabolic processing center
Nucleus
Cytoplasm: cytosol + organelles
Mitochondria are the source of many energy pathways
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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
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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
Breakdown and Release of Energy
Extracting energy from carbohydrate
Glycolysis
Pathway splits glucose into two pyruvates
Transfers electrons to NAD
Produces some ATP
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Breakdown and Release of Energy
Extracting energy from carbohydrate
Pyruvate to acetyl CoA
Releases CO2
Transfers electrons to NAD
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Breakdown and Release of Energy
Extracting energy from carbohydrate
Citric acid cycle
Releases CO2
Produces GTP (like ATP)
Transfers electrons to NAD and FAD
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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
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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
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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
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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
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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
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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
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Special States
Feasting
Excess energy intake from carbohydrate, fat, protein
Promotes storage
Fat adipose tissue
Amino acids protein synthesis
Carbohydrate adipose tissue
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Special States
Fasting
Inadequate energy intake
Promotes breakdown
Prolonged fasting
Protects body protein as long as possible
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Debbie Liehs () - Text cut off
Special States
Fasting
Survival priorities and potential energy sources
Preserve glucose-dependent tissue
RBC, brain cells, central nervous system
Maintain muscle mass
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
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
Energy Balance
Energy intake vs. energy output
Energy equilibrium
Intake = output
Maintain weight
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Energy Balance
Positive energy balance
Intake > output
Gain weight
Negative energy balance
Intake < output
Lose weight
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Energy In
Regulation of intake
Internal cues
Hunger
Prompts eating
Satiation
Signals to stop eating
Satiety
Tells when you are ready to eat again
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Energy In
Regulation of intake
External cues
Appetite
Psychological desire to eat
Influenced by the eating environment
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Energy In
Control by committee
What stimulates our cues?
Internal, physiological response
Eating environment
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Energy In
Internal factors
Gastrointestinal sensations
Sense of fullness
Neurological and hormonal factors
Neuropeptide Y
Ghrelin
Leptin
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Energy In
External factors
Diet composition
Energy density, balance of energy sources, and form
Macronutrients
Sensory properties
Taste
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Energy In
External factors
Portion size
Super-size culture
Environment and social factors
Hypothalamus
Emotional factors
Hypothalamus
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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
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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
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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)
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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)
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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
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Body Composition
Assessing body fatness
DXA
Underwater weighing
BodPod
Skinfold measurements
Bioelectrical impedance
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Body Composition
Body fat distribution
Gynoid obesity (“pear”)
Excess fat in hips and thighs
Android obesity (“apple”)
Excess fat around abdomen
Waist circumference
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