Ingestive behaviours

Question 1

Definition of eating.

Answer 1

-> The action of taking SOLID FOOD in the mouth in order to nourish oneself…carried out by the insertion of foodstuff in the mouth, followed by mastication, swallowing and digestion… eating is not specifically the ingestion of non-food substances such as CLAY, CHALK and STONES… they also exclude such potential foodstuffs as BLOOD and URINE.

Question 2

Why do we need food?
What does regulation of eating involve?

Answer 2

• Fuel: energy supply
• Nutrition: essential chemicals
  > Bio/psycho/social factors

Question 3

What does hunger motivate?

Answer 3

• Food seeking behaviour, thoughts + emotions

Question 4

What is the biological interpretation of eating?

Answer 4

• Mechanical and chemical digestion after eating, and its sequential physical and chemical digestion by GIT.
  > Absorption of nutrients that help refuel the body and quench our need for more food

Question 5

What is the role of of the CNS in hunger perception?

Answer 5

• The hypothalamus - key controller of food intake

Question 6

What is the set point theory? What is wrong with this?

Answer 6

• Old fashioned : Long term regulation of body weight results from a complex integration of hormonal, metabolic and neural signals

Question 7

What are the appetite signals when you are:
1- Hungry
2- Fed
3- If we have more long term energy reservoirs present

Answer 7

1- Hungry: Gremlin from stomach
2- Fed: Glucose + Insulin (PYY+ CCK)
3- If we have more long term energy reservoirs present(adipose): LEPTIN and RETINOL BINDING PROTEIN 4 (Rbp4) in proportion to fat content which reduces insulin sensitivity

Question 8

Taste perception can be modulated by what?
Give examples

Answer 8

• Endocrine and chemokine messengers – suggesting that the state of the body alters our enjoyment of the food we ingest.

> Angiotensin II decrease sensitivity to salty tastes, but increases sensitivity to sweet tastes
Leptin increases sensitivity to sweet food
Insulin increases sensitivity to salty food
TNF-alpha decreases sensitivity to some bitter tasting foods
** (Decreased sensitivity → greater consumption)**

Question 9

What is Pica?

Answer 9

• A craving to ingest non-food stuffs is associate with a variety of micronutrient deficiencies (e.g. iron, zinc, phosphorous, vitamins B, C and D). The biological mechanisms behind this link to dietary deficiency is unclear.

Question 10

Why do we feel thirsty?

Answer 10

• Increases in plasma osmolarity and [Ang II] trigger feelings of thirst via stimulating subfornical organ (SFO) and the organum vasculosum of the lamina terminalis (OVLT)
  -> Modulatedby GI afferents and baroreceptor inputs.
• Median preoptic nucleus sends signals to the Insula (interoception) and cingulate cortex(motivation/emotional processing)

Question 11

1- What is sodium appetite?

2- What does sodium appetite require activation of?

Answer 11

1- Elicited by sodium depletion > increased palatability and drive to ingest salty substances

2- Activation of the RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM via aldosterone activated HSD2 neurones in the nucleus tractus solitarii

Question 12

HSD2 neurones are salt sensitive and activated by sodium depletion, Why are HSD2 neurones unique?

Answer 12

• Express MINERALCORITCOID RECPETORS (MR) which are nuclear receptors that can be activated by both aldosterone and corticosteroids

> Normal conditions, cortisol is present at X100 greater concentration than aldosterone and will therefore block aldosterone’s effect on the HSD2 neurons. However, these neurons also have another receptor called 11-beta-hydroxysteroid dehydrogenase-type 2 which can metabolise corticosteroids.

Question 13

What 3 models can explain our eating behaviour?

Answer 13

Question 14

Describe the developmental model which explains eating behaviours.

Answer 14

• Focus on development of food preferences emphasises the role of exposure + learning.
  > More likely to eat foods you have had previously and avoid novel foods (neophobia). What you are exposed so is dependent on cultural/ economical factors
  > Associative learning: Positive reinforcement (food as a reward) OR limiting/controlling exposure to certain foods can make them more attractive.
  > Social learning: Exposure to foods can be influenced by those around us e.g friends, family, peers, role models

= Acquisition + maintenance of eating habits is learned.

Question 15

What is the Barker hypothesis?

Answer 15

• Intrauterine growth restriction or a low birth weight might predispose children to obesity and metabolic syndrome.
  = The deprived fetus develops a phenotype to survive in a nutrient-poor environment (Thrifty phenotype hypothesis)
• Mismatch between the intra- and extra-uterine environment the neonate may be maladapted

Question 16

Describe the cognitive model and how it explains eating behaviours.

Answer 16

• Emphasises the role of our beliefs, values and attitude
  (Theory of planned behaviour) e.g. Behavioural attitudes > subjective norms & perceived control > intention &raquo_space; eating behaviour

Question 17

What is hedonic eating?
How does it explain overeating?

Answer 17

• Eating is highly pleasurable experience which activates the MESOCORTICOLIMBIC DOPAMINERGIC PATHWAY.

> Eating is driven principally by the needs of our bodies (homeostatic eating),
> BUT we choose to eat on the basis of foods we find highly pleasurable it is all based on the pleasure we expect our foods to bring.

• However, this can sometimes lead to overeating i.e comfort eating where we may consume food items as a way of medicating ourselves against the negative emotions elicited by chronic stress.

Question 18

What is the weight concern model and how does it explain eating behaviour?

Answer 18

• Emphasises the role of what food and weight means to people.
  > There could be symbolic significance e.g. Sunday lunch, friends or emotional conflict

Question 19

What is body dissatisfaction/dysmorphia?

Answer 19

• Distorted body size estimation (discrepancy between ideal body type and perceived body type is indicative of eating disorders.)

Question 20

What factors can cause body dissatisfaction?

Answer 20

Social factors
* Role of media - influence on young girls
* Ethnicity & social class - related to beliefs
* Family - mothers communicate own dissatisfaction to daughters

Psychological factors
* Beliefs - parents & personal
* Mother-daughter relationship - “enmeshed”

Question 21

Describe dieters behaviour? And explain why.

Answer 21

• Dieters often over & under eat (“yo-yo” dieting) causing weight fluctuation rather than loss:

1- Cognitive shift - breakdown in self control
> Motivational collapse - give in
2- Role of denial
> Paradoxical effect - suppressed thoughts become more salient (the more u try to avoid something the more you think of it)
3- Mood modification
> Eating elevates low mood
4- Over-eating as relapse
> Belief that behaviour is all or nothing. Lapse → relapse

Question 22

What can restrained eating be associated with?

Answer 22

• Body dissatisfaction
• Cravings
• Guilt about food/eating
• Low self esteem, anxiety & depression
• Overestimation of body size
• May also contribute to unhealthy eating & eating disorders

Question 23

Obesity is a product of a complex set of factors such as…

Answer 23

• Biological, e.g. genetic
• Social, e.g. food industry, family
• Behavioural, e.g.
• Under-exercise
• Diet higher in fat
• More responsive to food related cues?

Question 24

How can drugs e.g. marijuana lead to unhealthy eating?

Answer 24

• Contains tetrahydracannabinol
  which activates the **endocannibanoid receptor, CB1

> Activation of CB1 receptors enhance our appetite directly in the hypothalamus, as well as enhancing the release of the appetite stimulating hormone Ghrelin from the stomach, and inhibiting the release of the satiety signal cholecystokinin from the duodenum.
= strong appetite-stimulating effect

In addition, CB1 enhances our perception of reward for eating, as well as enhancing our sensory perception of fats and taste of sugary food – meaning we are likely to enjoy unhealthy foods more.

Question 25

How can the gut microbiome influence our eating behaviours?

Answer 25

• Gut bacteria are fed by the food we eat – they may control our eating preferences - DIFFERENCES IN MICROBIOME OF obese/thin people

> Different bacterial species thrive on different diets. (e.g. carbohydrate – Prevotella; Fats – Bacteriodetes)

> Bacterial byproducts can affect mood in animals

> Bacteria can also trigger enteric nervous to signal to the vagus – which might be able to affect our eating behaviour

Question 26

What are some eating disorders?

Answer 26

• Anorexia
• Bulimia
• Binge Eating Disorder
• Other Specified Feeding or Eating Disorder (OSFED)
• Rumination disorder
• Pica
• Avoidant/Restrictive food intake disorder (ARFID)

Question 27

Compare Bulimia nervosa and Anorexia Nervosa.

Answer 27