Metabolism
Feasting
• Feasting adds to body stores of
carbohydrate and fat
– Excess carbohydrate used to fill
glycogen stores excess glucose stored
as fat
– Excess fat stored as fat
– Excess protein remove N and store as
fat
Fasting – Glycogen Available
• Draw upon stores during fasts (even
short-term) and during exercise
– Liver glycogen blood glucose energy
for all cells
– Muscle glycogen muscle glucose
energy for muscle cells
Fasting – Glycogen Available
• Draw upon stores during fasts (even
short-term) and during exercise
– Fat stores fatty acids in blood provide
energy for all cells, but brain and CNS
Fasting – Glycogen Stores
EMPTY
• Only protein and fats are available as a
source of energy
– See board!
Estimating Energy Needs
Body uses energy for:
1. Basal metabolism
2. Thermic effect of food
3. Physical activity
Basal Metabolism
• Basal metabolism
– Energy needed to maintain the body at
complete rest (physical, emotional, and
digestive)
– Largest component of daily energy
expenditure
Basal Metabolism
• Basal Metabolic Rate (BMR)
– # kcal burned per hour per kg body
weight
Basal Metabolism
• BMR impacted by:
– Lean body mass
• More LBM, the higher your BMR
• More fat, the lower your BMR
– Age and gender (related to LBM)
• BMR slows with age
• BMR higher in males
Basal Metabolism
– Height
• Taller, thinner people have a higher BMR
• More surface area to support
– Fever raise BMR
• 10 F fever raises BMR by 7%
– Fasting and malnutrition lower BMR
Basal Metabolism
– Smoking and caffeine raise BMR
– Stress raises BMR
Thermic Effect of Food
• TEF – energy needed to digest, absorb,
transport, and metabolize nutrients
– Smallest component of daily energy
expenditure
– ~ 10% caloric intake
Physical Activity
• Physical Activity – energy needed to
support voluntary activity
– Energy required impacted by:
• Muscle mass
• Body weight
• Nature of activity
– Duration, intensity, frequency
Energy Expenditure
• Summary
– To maintain energy balance, energy input
must balance energy expenditure
– Expend energy to:
• support basal metabolism]
• process foods (TEF)
• support physical activity