Hunger and Eating

Question 1

Whats the obese survival?

Answer 1

Obese people survive certain procedures more because they have extra weight to lose.

Question 2

Why do we eat? Why do we start/stop eating?

Answer 2

Past: maintain an energy balance in our bodies. to satisfy a deficit in our body’s energy reserves.. NOT TRUE.

Question 3

What’s homeostasis?

Answer 3

Wisdom of the body (cannon)
Necessary condition for free life is constancy of internal environment.
- temp/glucose/salt/water

Goal: maintain a set point.
Low levels: internal changes (vasopressin released to retain water)
High levels; behavioral changes (go get a drink of water)

Question 4

What are the two mechanisms related to homeostasis?

Answer 4

Glucostatic (short term)
-eat when blood sugar is low
Lipostatic (long term)
- seek more food over time if you have higher body fat

Question 5

Is hunger triggered by changes in blood sugar.

Evidence?

Answer 5

Prior to a meal, blood sugar decreases, subjective feeling of hunger. if you skip that meal, blood sugar goes back up!

more or less preparing for a meal instead. Food is stressful on the body.

Anorexic people have hard time eating cause they haven’t had that opponent process/preparatory response for food.

INSULIN: used to stimtulate eating, (inject insulin, decreases blood sugar levels) BIG decrease causes eating. HOWEVER this never would happen in the actual wild. only at EXTREME levels.
AND if you DRINK SUGARY drink before a meal, you still eat the same amount!!!

Question 6

Is hunger triggered by changes in body fat?

Answer 6

Leptin: in adapose cells, in fatty tissues. Leptin increases metabolism and decreases hunger. When you have damaged leptin, animals eat excessively and get really fat.

HOWEVER overactivating leptin doesn’t actually work in the human body.

Larger people with more fat don’t eat less. Maybe they’re less sensitive to the leptin??

Question 7

Are there other body/brain mechansims for initiation/cessation of eating?

Answer 7

Ghrelin: hunger hormone released from stomach. If you knock it out it doesn’t actually work to lose weight.

Orexin: in hypothalamus, (aka hypocretin) initiate eating. It works if you make an antagonist however it interacts with sleep

Peptide YY: in digestive tract, sends a full signal. works for weight loss but interacted with the heart.

Question 8

What is the dual hypothalamic theory of hunger? Why is it problematic?

Answer 8

Lateral hypothalamus: stimulated: eat excessively, lesioned, see aphagia and adipsia

ventromedial hypothalamus: stimulated- stop eating
lesion: overeats.

Double dissociaton

However issues:

1. electrolytic lesions are messy and aren’t really used anymore. Hit medial forebrain bundle.
2. caused a loss of eating and all other spontaneous activities. stop “doing” not just stop “eating” - mesolimbic dopamine pathway
3. damaging VMH, causes increase in insulin which could contribute to why animals eat so excessively. Can’t release energy and use body fat.

Evidence isn’t ideal.

Question 9

Do we chose our diet in an intelligent way?

Answer 9

Homeostatic eating:
1. Salt deprived animals will chose salty foods (diabetes insipidus)
and
2. if given a cafeteria diet, people will eat balanced diet.

Until something delicious is available
- people sample from that thing way too much. no longer intelligent EVEN if they’re at a deficit for a specific thing (protein deprived animals)

Question 10

Is caloric restriction intelligent in humans?

Answer 10

It benefits us in the long run, in resus monkeys old monkeys have less age related morbidity. Bad things higher in free feeding group.
Famine is the norm in most species, in a stabel environment you’ll eat whatever is available to you .

Question 11

Are body weights stable?

Answer 11

Body weights are not stable, this shows lipostatic mechanism doesn’t work, cause when people are fat they just get fatter.
in all countries proportion overwieght is going up

Question 12

Does stimuli that are not physiologically relevant influence our eating?

Answer 12

They do!

• friends and food (60% more)
• Friends and bitterness (eat bitter in social environments)
• culture and preference food (spice sugar salts etc)

Question 13

What else contradicts homeostatic theories of eating?

Answer 13

Bottomless bowl of soup
Appetizer effect (actually eat more) 
Sham eating (disconnect stomach from esophagus) - eat a normal amount at first 
Eating in anterograde amnesia 
Significance of serving size 
Lots of noodles??

Question 14

What is not true for homeostatic theory?

Answer 14

Hunger/eating triggered by changes in blood sugar/body fat
Starting/stopping eating triggerd byt e above ^
There must be other mechansims for starting these behaviors
We should know what to eat and when
BOdy weights should be stable
Other factors shouldn’t influence eating
Taste flavour should be unimportant

Question 15

What are evolutionary pressures on eating?

Answer 15

Fat Bear!
The norm is food scarcity, so eating lots and then having nothing is the norm.
Satiety signals are weak (like in bears)
- to survive in the lean times.
Deal with low calorie conditions

Question 16

What is eating driven by if not homeostatic processes?

Answer 16

Positive incentive theory of eating.
- we want to eat what brings us pleasure / anticipated pleasure
The amount of hunger you feel depends on interaction between lots of factors
- flavour of food
- what you know about it
- time since last meal
- type and quantity of food recently consumed
- presence of other people
- blood glucose levels

Taste: sweet sour salty bitter umami (we like high energy high salt foods)

AKA: you EAT WHEN YOU NORMALLY EXCEPT FOOD.
- combo of evolutionary pressures and simple learning.

Question 17

What are the evolutionary and simple pressures of eating?

Answer 17

Evolutionary

• we avoid dangerous foods
• we choose trustworthy foods
• we eat a variety of foods
• eat way more than we need

Simple Learning

• eat what brings pleasure
• eat what has been associated with pleasure in the past
• seek food at times when we learned food will be present.

Question 18

Do we avoid dangerous foods and choose trustworth foods?

Answer 18

Yes! In the short term.
- flavour often corresponds to value/safety. social transmission of food preference (rats will eat foods that other rats have eaten - just based off of smell) because they’re neophobic.

HOWEVER

foods that taste good and are “trustworthy” are bad for us in the long term!
- pizza is good and we trust it, motivated to seek it (dopamine)

Question 19

Do we eat a variety of foods?

Answer 19

Yes! Cafeteria diets (number of flavours and number of SHAPES also influence how much you’ll eat. This means its happening at PERIPHERAL and CENTRAL level (cause shapes and flavours effect it)

Sensory Specific Satiety: as you consume, you’ll want less of that item.
- can’t be explained by homeostatic mechansims, but makes sense evolutionary, because you need to eat what is available now and you need a variety. Don’t want to be “full” when a new food comes around.

This is affected by personal preference.

Question 20

Do we eat far more than we need?

Answer 20

Yes. Appetizer effect, social factors, buffets,

feast or famine strategy, this is really good!!
Body weight goes up with cafeteria type diets

Question 21

Do we eat what brings us pleasure?

Answer 21

Yes. We like certain tastes more.

also: Learning is usually a slow process, but one bad experience and we won’t eat that food again.
Rapidly learned food aversions. Noxious experiences.

Example:
double dissociation

6-OHDA: kills dopamine neurons - shows appetitive adn aversive faces but won’t seek the food

Nalozone injection (opiod antagonist) they don’t show faces but they seek food still.

^^difference between pleasureable experience and motivational processes.

Question 22

Do we eat what has been associated with pleasure in the past?

Answer 22

Pleasure: socialization. Bitterness is better than neutral when paired with socialization (Coffee and beer) Other social factors like Spicy food: culturally bound
Reinforcing properties other than the actual taste/ smell.
We aren’t hungry due to energy deficit, we’re hugry cause its when we usually eat.

Question 23

Do we seek food at times when food is predicted to be present?

Answer 23

Yes. Trained animals on a buzzer/light, and then when free feeding they still eat when the buzzer comes along!!
For humans: that’s when they’re expecting food (time of day or getting home from work or something)

Question 24

If there is a pleasure molecule what is it?

Answer 24

likely opiods ahah don’t worry about his this is adumb quesiton lolol