Appetite regulation and obesity Week/Lecture 1

Question 1

explain basic appetite regulation
- models
- motivation

Answer 1

• ‘typical’ appetite regulation
  
  • Early models based on homeostatic principles
  • Motivated to maintain absence of hunger
  • Eat until homeostasis is restored

Question 2

what are the central mechanisms for appetite

Answer 2

• Hypothalamus
  
  • Brainstem
  • Endocannabinoids

Question 3

what do the central mechanisms for appetite do?

Answer 3

• (promote search for food; aim to lay down fat, inhibit hunger)

Question 4

2 types of peripheral mechanisms for appetite regulation

Answer 4

episodic factors
tonic factors

Question 5

episodic factors in appetite regulation

Answer 5

in response to a meal
Stomach, intestines, blood, hormones (leptin = satiety, ghrelin = hunger) (leptin = ‘thin’)

Question 6

tonic factors in appetite regulation

Answer 6

○ Monitor energy levels and storage
○ Adipose tissue, immune system, related hormones

Question 7

Appetite complex CCK
- what is it
- how does it work

Answer 7

• Cholecystokinin: CCK - potent satiety signal
  
  • Released by stretch receptors in stomach and received by brainstem/hypothalamus

Question 8

Ob/ob mice and leptin
- what was found

Answer 8

• Correlates with adiposity and increases with increasing levels of body fat
  
  • Causes dramatic weight lose in mice
  • Leptin gene mutation are rare in human population

Question 9

2018 study on leptin resistance and obesity

Answer 9

Destructive mechanism blocks brain from knowing when to stop eating

• Destructive mechanism at molecular level
  
  • Causes phenomenon associated with obesity: Leptin resistance
  • Mice fed high fat diet produce enzyme MMP-2 that clips receptors leptin from the surface of neuronal cells in hypothalamus
  • This blocks leptin binding to receptors
  • This keeps neurons from signalling that stomach is full and you should stop eating

Question 10

what controls hunger?

Answer 10

• Biological factors (internal controls)
  
  • Moderated by environmental (food cues) and psychological (e.g. mood) factors
  • The absence of fullness (Peter Rogers)

Question 11

what do satiation and satiety do

Answer 11

inhibit food intake

Question 12

satiation

Answer 12

• Satiation = within-meal process (stops you eating more during a meal)

Question 13

satiety

Answer 13

• Satiety = inhibits intake after termination of a meal (stops food seeking behaviour - theoretically longer after a bigger meal)

Question 14

satiation as a complex process

Answer 14

(Le Magnen, 1992)
○ Analogy with ST and LT memory
○ Several sensory systems at play (explains the ‘different stomachs’ for different foods)

Question 15

obesity definitions
- adiposity
- body fat
- waist-hip

Answer 15

• Excess adiposity: high amount of body fat to lean mass
  
  • Percentage body fat (skinfold > bioelectrical impedence)
  • Waist circumference/waist-hip ratio (WHR) - fat deposition around abdomen better predictor of comorbidities such as CVD, T2D (than BMI)

Question 16

effects of obesity

Answer 16

○ Reduced life expectancy
○ CVD
○ T2D
○ At least 12 kinds of cancer
○ Liver disease
○ Respiratory disease
○ etc

Question 17

impact of SES and environmental factors on obesity

Answer 17

• Low socioeconomic status
  
  • Money
  • Physical geography
  • Opportunity
  • Access
  • Safety (physical activity) - less play outside can mean more TV/internet inside
    McCarthy 2022 influence of unhealthy food and beverage marketing through social media

Question 18

factors impacting societal norms around portion size

Answer 18

• Implicit; gradual increase
  
  • Explicit; ‘super-size me’
  • Evidence for meal planning in humans (90% of time)
  • Engage in plate cleaning behaviour 90% of the time