5. Appetite

Question 1

Digestion

Answer 1

Food is broken down by our gut microbiome (bacteria and other organisms in our intestines) and we absorb nutrients from it

Question 2

Forms of Energy

Answer 2

Lipids - fats
Amino acids - proteins
Glucose - sugar from carbs

Question 3

Energy storage

Answer 3

Fat (main, more energy per gram)
Glycogen
Proteins

Question 4

3 Stages of Metabolism

Answer 4

Cephalic phase
Absorptive phase
Fasting phase

Question 5

Cephalic phase

Answer 5

Sight/smell of food
Ends with absorption of nutrients into bloodstream
A lot of insulin, small amounts of glucagon

Question 6

Absorptive phase

Answer 6

Energy is absorbed, body’s immediate needs are met
A lot of insulin, small amounts of glucagon

Question 7

Fasting phase

Answer 7

The body withdraws energy from its reserves
Energy from the previous meal has been used up
Ends at the beginning of the next cephalic phase
High glucagon levels

Question 8

Skipping of fasting phase

Answer 8

Fast weight gain occurs

Question 9

Metabolic Phases/Cycle (hormones)

Answer 9

1. Insulin is released
   Enabling glucose to enter cells
   Fuel conversion for storage is promoted
2. Blood glucose levels decline, insulin stays the same
3. Rapid return of hunger
   Insulin levels are low, so glucagon cannot enter cells
   Glucagon goes to the brain instead, stopping it from being the body’s main energy source
   Free fatty acids are used as the main source

Question 10

Hunger related hormone

Answer 10

Galanin - triggers hunger for fats
Ghrelin

Question 11

Ghrelin

Answer 11

Neurotransmitter, binds to the same receptors as growth hormones
Increases hunger

Question 12

Galanin

Answer 12

Hunger related hormone
Triggers hunger for fats

Question 13

Satiety Related Hormones

Answer 13

CCK
Leptin

Question 14

CCK - satiety related hormone

Answer 14

In the short-term

1. Constricts the sphincter muscle, leading to the stomach being constricted and filling more quickly
2. Stimulates the vagus nerve, sending signals to the hypothalamus, signals satiety

Question 15

Leptin - satiety related hormone

Answer 15

Satiety related hormone

Function is to decrease appetite and increase fat metabolism

Released after meals

Question 16

Orexin/Hypocretin - hunger related hormone

Answer 16

Released in the hypothalamus

Two roles in feeding
Increase in seeking food
Reward response

Question 17

Sensory specific satiety

Answer 17

The number of different tastes influences meal size
More tastes = eating more

Question 18

Cafeteria diet

Answer 18

Positive incentive value
Satisfied with one food but still crave other tastes

Question 19

Set-point theory

Answer 19

The motivation to eat comes from energy deficits, eating is a method of returning to our normal levels of energy

We eat until this ‘set-point’ is obtained/we reach homeostasis

Lots of evidence against

Question 20

Criticism of set-point theory

Answer 20

Inconsistent with basic related evolutionary theories
That we eat as much as possible to survive

Obesity

Unaccounted for:
Tastes
Social influences

Question 21

Appetizer Effect

Answer 21

Hunger is increased after eating appetizers as the cephalic phase responses are increased

Question 22

Lateral Hypothalamus

Answer 22

Releases orexin, making you seek food
Controls insulin secretion
Alters taste responsiveness, enhancing the taste of food

Question 23

Paraventricular Hypothalamus

Answer 23

Gathers all information and provides it to the lateral nucleus
Inhibitory effect

Question 24

Sham eating experiments

Answer 24

Food is chewed and swallowed but not taken to the stomach, redirected by a tube inserted into the body
If set-point was true, the rats would’ve eaten huge meals as the energy threshold was not being met but this was not the case
Rats ate a relatively normal amount of food
After several meals, rats ate more
Showed that people enjoy physical eating

Question 25

Causes of Obesity

Answer 25

Related to taste preferences, cephalic responses, culture, genetic factors (predisposition) etc.
Drugs
Surgeries
Differences in energy expenditure
Not everyone exercises the same amount
Differences in the basal metabolic rate in each person
Diet induced thermogenesis
Social influences

Question 26

Diet induced thermogenesis

Answer 26

Mechanism by which the body adjusts the efficiency of energy utilization in response to body fat
Less body fat - more efficient energy usage

Question 27

Leaky Barrel Model

Answer 27

There has to be balance between all factors
(food intake, energy expenditure, satiety signals etc.)
Remember the image with the hole in the barrel & the barrel on the hose

Question 28

Glucostatic set-point theory

Answer 28

The set-point involves glucose intake
Short-term (energy)?

Question 29

Lipostatic set-point theory

Answer 29

Lipid set-point
Long-term (energy?)
Evidence: adults body weight is relatively consistent

Question 30

Conditioning

Answer 30

Conditioned taste aversion, can determine what we do and don’t eat

Question 31

Preferences

Answer 31

High calorie foods like sweets (reminiscent of Mother’s milk)
Foods high in minerals and vitamins (usual choice but with so many options our bodies find it hard to differentiate and choose the best one)

Question 32

Arcuate Nucleus

Answer 32

One set of hunger neurons and one set of satiety neurons that affect the paraventricular nucleus

Question 33

Paraventricular Nucleus

Answer 33

Output stimulates satiety

Question 34

Lateral Nucleus

Answer 34

Output stimulates feeding

Question 35

Ventromedial hypothalamus

Answer 35

Output inhibits feeding