Energy in Food and BMR

Question 1

Macronutrition is the study of

Answer 1

obtaining energy to fuel normal activity

Question 2

Faulty nutrition (under and over) is a major cause of

Answer 2

disease, along with infection and inherited abnormalities

Question 3

A typical adult needs how many MJ of dietary energy per day?

Answer 3

10MJ

Question 4

How does dietary energy leave the body?

Answer 4

10MJ of energy taken up per day is radiated as heat (100W) regardless of the work performed

Question 5

What is the BMR?

Answer 5

a measurable quantity that is the minimum energy to sustain life; energy to pump blood, sustain cellular processes, and minimal metabolic activity to maintain 37 degrees body temperature

Question 6

Exercise is usually what % of typical daily energy expenditure?

Answer 6

20-40%; critical for health and weight control

Question 7

What is a bomb calorimeter?

Answer 7

it gives a direct measure of the energy of combustion in food to H2O, CO2, NO, and heat; food is combusted under pressurized oxygen in a chamber and the amount of heat released is measured

Question 8

What is an Atwater chamber?

Answer 8

70kg male medical student in a chamber; over 4 days measured daily averages in MJ of energy content of food, energy supplied from body reserves (fat and protein), faecal and urinary waste energy; calculated the energy obtained from food and depletion of reserves and the heat output - 10MJ per day

Question 9

1 Watt =

Answer 9

1 joule/sec (100W radiated per day)

Question 10

What is the first law of thermodynamics?

Answer 10

energy can neither be created nor destroyed, only transformed - the energy of sunlight becomes the stored chemical energy of glucose which we eat

Question 11

Fat produces how many kJ/g?

Answer 11

37

Question 12

Alcohol produces how many kJ/g?

Answer 12

30

Question 13

Carbohydrates produce how many kJ/g?

Answer 13

17

Question 14

Protein produces how many kJ/g?

Answer 14

16

Question 15

Alcohol is metabolised to

Answer 15

acetate by alcohol dehydrogenase and aldehyde dehydrogenase; becomes Acetyl-coA

Question 16

BMR takes up how much energy per day?

Answer 16

60-70% (6-7MJ)

Question 17

Specific dynamic effect

Answer 17

aka postprandial thermogenesis, heat increment of feeding, diet induced thermogenesis; 8-10% of energy turnover (elevated by high protein diet) ie expended in absorption and transport of nutrients, digestive enzyme synthesis, gut mobility, and gut replacement

Question 18

BMR is measured

Answer 18

in subjects at rest 12 hours after eating in a thermoneutral environment of 25-30 degrees C

Question 19

Thermal efficiency is determined by

Answer 19

a lower area/volume; larger bodies are more efficient (have lower BMR)

Question 20

How does age affect BMR?

Answer 20

newborns use about 15% of energy for growth; children have higher MR due to size and growth; adult BMR decreases by 2% every 10yrs after age 20

Question 21

What affect does high body fat have on BMR?

Answer 21

high body fat decreases BMR; fat cells need little energy to store TAGs tf high fat = low energy consumption and greater insulation to heat loss

Question 22

Why do females have lower BMR?

Answer 22

higher adiposity (20-30%) for reproductive health

Question 23

Why do males require more energy per day?

Answer 23

Leaner body mass, requires ~1MJ more energy