Energy Expenditure

Question 1

What is the formula for energy balance, and what components does it include?

Answer 1

Energy balance = energy intake - energy expenditure
Components: carbohydrates, lipids, proteins, alcohol (intake), basal metabolic rate, physical activity, thermic effect of food, thermoregulation (expenditure).

Question 2

How is energy intake assessed, and what methods are commonly used for this purpose?

Answer 2

Assessed through calories consumed.
Methods: 24-hour recalls, food records.

Question 3

What are the main factors influencing basal metabolic rate (BMR)?

Answer 3

Includes respiration, heartbeat, renal function, muscle tone, blood circulation.
Organs like liver, lung, heart, brain, kidneys contribute to 60-80% of basal metabolism.
Muscle contributes ≤ 25% of basal metabolism.

Question 4

How is BMR assessed, and what conditions are considered during measurement?

Answer 4

Measured by consumed O2 and produced CO2 under standardized conditions.
Conditions: postabsorptive state, ideally after awakening, lying down, relaxed, motionless, and at a comfortable temperature.

Question 5

What is Resting Metabolic Rate (RMR), and how does it differ from BMR?

Answer 5

RMR is measured under conditions similar to BMR but without food intake or exercise 4-5 hours before the test.
RMR is 10% higher than BMR, considering the calories needed for digesting foods.

Question 6

What are the factors influencing BMR and RMR related to age and body composition?

Answer 6

Highest BMR during infancy due to growth.
BMR decreases with maturation.
In adults, BMR decreases with age, influenced by changes in fat-free mass and fat mass.

Question 7

How does gender impact BMR, and what is the observed difference between men and women?

Answer 7

Men have a 10% higher BMR than females.
Men: 1 kcal/kg/hr; Women: 0.9 kcal/kg/hr due to different body compositions.

Question 8

What physiological states influence BMR and RMR?

Answer 8

Pregnancy, fever, hyperthyroidism, fasting, menstrual cycle.

Question 9

Define Thermic Effect of Food (Diet-Induced Thermogenesis).

Answer 9

It’s the metabolic response to food, leading to increased heat production after a meal.
Involves digestion, absorption, active transport, metabolism, and storage of energy from ingested food.
Constitutes 5-30% increase in energy expenditure over BMR.

Question 10

What are the contributions of different macronutrients to the Thermic Effect of Food?

Answer 10

Greatest effect for protein (20-30% increase in energy expenditure).
Intermediate effect for carbohydrates (5-10%).
Smallest effect for fat (0-5%).

Question 11

Define Thermoregulation (Regulatory Thermogenesis) and its impact on energy expenditure.

Answer 11

It’s the change in metabolism to maintain or restore the body’s core temperature.
Environmental temperature changes lead to alterations in energy expenditure.
Hypothermia and hyperthermia are examples of extreme responses to environmental temperature changes.

Question 12

How does environmental temperature impact thermoregulation?

Answer 12

In a cold environment, the body generates heat, contributing to increased energy expenditure.
In a warm environment, reduced muscle tonus and sweating contribute to altered energy expenditure.

Question 13

What is the role of physical activity in energy expenditure, and how variable is it among individuals?

Answer 13

Physical activity is the most variable component, accounting for 20-40% of total energy expenditure.
It depends on factors like intensity, duration, and frequency of activity.

Question 14

How are methods like calorimetry used to assess energy expenditure?

Answer 14

Calorimetry involves the determination of body heat loss.
Direct calorimetry measures heat dissipation, while indirect calorimetry measures oxygen consumption and carbon dioxide expiration.

Question 15

What is Respiratory Quotient (RQ), and how is it used in indirect calorimetry?

Answer 15

RQ = CO2 produced / O2 inhaled.
It’s used to calculate macronutrient composition, with different values for carbohydrates, fat, and protein.

Question 16

Explain the Doubly Labeled Water method and its application in assessing energy expenditure.

Answer 16

It involves adding stable isotopes to water and measuring their disappearance in blood and urine.
It helps calculate energy expenditure by assessing the turnover rates of labeled oxygen and hydrogen.
Despite its accuracy, it has limitations such as high costs and potential errors in food records.

Question 17

What are the limitations of direct calorimetry, and why is indirect calorimetry more commonly used?

Answer 17

Direct calorimetry is expensive, laborious, and uncomfortable for subjects.
Indirect calorimetry, measuring oxygen consumption and carbon dioxide expiration, is more practical and less invasive.

Question 18

What is the significance of the Respiratory Quotient (RQ) in different physiological conditions?

Answer 18

RQ can indicate the form of energy expenditure, such as BMR or thermic effect of food.
Different RQ values represent different macronutrient compositions and metabolic states.

Question 19

How is the Doubly Labeled Water method applied in assessing energy expenditure, and what are its limitations?

Answer 19

It involves adding stable isotopes to water and measuring their disappearance in blood and urine.
Limitations include the reliance on food records

Question 20

Define energy balance.

Answer 20

Energy balance is achieved when energy input, derived from food and beverages, equals energy output, which includes metabolism, organ function, regulation of body temperature, and exercise.

Question 21

What is negative energy balance, and what are its causes?

Answer 21

Negative energy balance occurs when energy intake is less than energy expenditure. Causes include insufficient food availability, anorexia nervosa, bulimia nervosa, and certain medical conditions like cancer.

Question 22

Explain the female athlete triad and its management.

Answer 22

The female athlete triad involves disordered eating, irregular menstruation, and low bone density, often seen in young female athletes. Management includes reducing preoccupation with food, achieving a healthy weight, and decreasing training intensity.

Question 23

What characterizes positive energy balance?

Answer 23

Positive energy balance occurs when energy input exceeds output, leading to the gain of adipose tissue, muscle, and weight. It can result from excessive caloric intake, a sedentary lifestyle, or genetic/biochemical factors.

Question 24

How can exercise impact energy balance?

Answer 24

Exercise contributes to negative energy balance, benefiting weight loss in overweight individuals. However, it may be detrimental to individuals with certain eating disorders or conditions like bulimia nervosa or the female athlete triad.

Question 25

What role does dietary composition play in body weight regulation?

Answer 25

Dietary composition, including high-fat and sweetened foods, can impact body weight. Processed foods and increased sugar-sweetened beverage intake are correlated with weight gain.

Question 26

How do portion size and meal frequency affect body weight?

Answer 26

Larger portion sizes and irregular meal patterns are associated with obesity. Omitting meals, especially breakfast, is linked to obesity-related behaviors.

Question 27

Describe the regulation of hunger and satiety by hormones.

Answer 27

Hormones like ghrelin stimulate hunger, while cholecystokinin, insulin, leptin, and PYY decrease hunger. The hypothalamus, particularly the arcuate nucleus, plays a key role in regulating these hormones.

Question 28

What are genetic influences on body weight, and give examples?

Answer 28

Over 127 candidate genes are associated with obesity, including the melanocortin receptor and the fat mass and obesity-associated gene (FTO). Heritability influences body weight, but the role of genes like the leptin receptor remains inconclusive.

Question 29

How does exercise impact energy expenditure, and what are its benefits?

Answer 29

Physical activity contributes to negative energy balance and can account for 20-40% of energy expenditure. It is beneficial for weight loss in overweight individuals but may pose challenges for those with eating disorders or the female athlete triad.

Question 30

Define fat body mass and fat-free body mass.

Answer 30

Fat body mass includes triacylglycerides and lipids, while fat-free body mass comprises water, muscle, bone, connective tissue, and organs. Lean body mass is fat-free mass plus essential fats.

Question 31

What are the methods for measuring body composition?

Answer 31

Methods include anthropometry (skinfold thickness), densitometry (underwater weighing), absorptiometry (dual-energy X-ray absorptiometry), bioelectric impedance analysis, and total body water measurement using stable isotopes.

Question 32

Describe anthropometry’s role in measuring body composition.

Answer 32

Anthropometry measures skinfold thickness and waist circumference, correlating with regional body fat distribution. Waist circumference is a predictor for heart disease risk.

Question 33

How does densitometry work, and what is its advantage and challenge?

Answer 33

Densitometry, such as underwater weighing, measures body fat by density. It is non-invasive and precise but faces challenges like high equipment cost and subject cooperation.

Question 34

Explain bioelectric impedance analysis and its challenges.

Answer 34

Bioelectric impedance analysis measures electrical conductivity, correlating with electrolyte and water content. Challenges include expensive equipment and readings affected by hydration and electrolyte imbalance.

Question 35

What is BMI, and what does it measure?

Answer 35

BMI, or body mass index, is a measure of body composition calculated as weight in kilograms divided by the square of height in meters. It is an approximate indicator of body fat.

Question 36

Summarize the methods for measuring body composition.

Answer 36

Fat body mass is measured by anthropometry, densitometry, and dual-energy X-ray absorptiometry. Fat-free body mass is measured by total body water, bioelectric impedance analysis, and dual-energy X-ray absorptiometry.

Question 37

How does BMI correlate with direct measures of body fat?

Answer 37

BMI correlates with direct measures of body fat, such as underwater weighing and dual-energy X-ray absorptiometry. It is an indirect parameter for body fat, widely used for health risk classification.

Question 38

What are the components of fat-free body mass?

Answer 38

Fat-free body mass includes water, muscle, bone, connective tissue, and organs. Lean body mass is fat-free mass plus essential fats.

Question 39

What challenges are associated with body composition measurement methods?

Answer 39

Challenges include potential errors in obese subjects, high equipment costs, and the impact of hydration and electrolyte imbalance on readings. Each method has its advantages and limitations.