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Questions and Answers
The indirect measurement of metabolic rate involves calculating heat based on the oxidation of _______.
mixed food (CHO + Fat + Proteins)
What is the definition of metabolic rate?
The amount of energy (heat) production per hour.
Specific Dynamic Action (S.D.A.) refers to the power of food to decrease metabolic rate.
False
Which factor causes the most marked increase in metabolic rate?
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How long after eating does metabolic rate begin to increase due to Specific Dynamic Action?
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What temperature is associated with the maximum Specific Dynamic Action?
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The Basal Metabolic Rate (B.M.R.) is measured under _______ conditions.
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Which of the following factors can increase Basal Metabolic Rate?
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At what rate do newly born infants have their B.M.R. per square meter?
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What effect does prolonged ingestion of proteins have on B.M.R.?
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B.M.R. is always higher in hot climates than in cold climates.
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Study Notes
Metabolic Rate
- The amount of energy (heat) an organism produces per hour
- Direct Measurement: Calorimeter (measures heat production directly).
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Indirect Measurement: Uses oxygen consumption to calculate heat production.
- 1 liter of oxygen used = 4.8 Kcal of energy released
- The amount of oxygen used is multiplied by 4.8 Kcal/liter.
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Factors Affecting Metabolic Rate:
- Exercise: Most significant increase.
- Eating: Especially protein intake.
- Exposure to Cold: Shivering increases metabolic rate.
- Endocrine Factors: Catecholamines (epinephrine, norepinephrine) and thyroxine (thyroid hormone) increase metabolic rate.
- Emotional State: Anxiety increases catecholamine release and muscle tone, raising metabolic rate.
- Starvation: Decreases metabolic rate due to decreased sympathetic activity and thyroxine production.
Specific Dynamic Action (SDA)
- The increase in metabolic rate after eating.
- Peaks 3-4 hours after eating.
- Returns to basal level within 12-18 hours.
- Causes: Metabolic processing of the food in the liver.
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Factors Influencing SDA:
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Type of Food:
- Protein: 30% of caloric value contributes to SDA.
- Carbohydrates: 6% of caloric value contributes to SDA.
- Fats: 4% of caloric value contributes to SDA.
- Quantity of Food: More food means greater SDA.
- External Temperature: SDA is highest at 33°C and absent at 3°C.
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Type of Food:
Basal Metabolic Rate (BMR)
- The energy production per hour under basal conditions:
- Complete physical and mental rest.
- Post-absorptive state (12-14 hours after last meal).
- Comfortable external temperature (20-25°C for clothed individuals, 28-31°C for naked individuals).
- Expression: Calories per hour per square meter of body surface area under basal conditions.
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Factors Affecting BMR:
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Physiological:
- Age: Decreases with age, except in newborns.
- Sex: Lower in females than males due to lack of androgens and greater fat stores.
- Physical Habits: Athletes have higher BMRs due to muscle mass and lower fat content.
- Dietetic Habits: Prolonged protein intake slightly increases BMR.
- Climate: Higher BMR in cold climates, lower BMR in hot climates.
- Race: Pure and dark races have lower BMRs than mixed races.
- Sleep: Decreases BMR due to decreased muscle tone and sympathetic activity.
- Pregnancy: Increases BMR due to increased thyroid activity and fetal metabolism
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Pathological:
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Increases BMR:
- Hyperthyroidism
- Hyperpituitarism
- Hyperfunctioning adrenal medulla
- Fever
- Heart failure
- Blood diseases
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Decreases BMR:
- Hypothyroidism
- Hypopituitarism
- Hypofunction of adrenal cortex
- Hypothermia
- Prolonged starvation and malnutrition
- Diabetes insipidus
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Increases BMR:
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BMR Values
- Newborn Infants: 25 Kcal/h/m2
- 2-5 Years: 60 Kcal/h/m2
- Puberty: 55 Kcal/h/m2
- 20 Years: 40 Kcal/h/m2
- After 20 Years: Decreases by 1 Kcal/h/m2 every 10 years.
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Description
Explore the intricacies of metabolic rate and how various factors like exercise, diet, and emotional state influence it. Learn about direct and indirect measurement techniques, as well as the concept of Specific Dynamic Action (SDA) that occurs after eating. This quiz will test your understanding of energy production in organisms.
