Volume, variety and sensory specific satiety - week/lecture 6

Question 1

biology behind hunger

Answer 1

• Months of energy stored in adipose tissue; short-term fasting has little impact on energy stores
  
  • Energy continues to be supplied to the body’s tissues through a variety of fuels (fats, glycogen, ketones), from different sources, depending on the duration of the fast

Question 2

• Rogers and Hardman (2015) - what do individuals explain their perceptions of hunger as?

Answer 2

○ When full, individuals explained their perceptions of hunger in relation to their level of fullness since their last meal, the timing and/or size of the previous meals, and the proximity of their next meal

Question 3

what is the expression of hunger?

Answer 3

• The expression of hunger is actually grounded in absence of fullness; and it is this that underlies the readiness to eat (Rogers & Brunstrom, 2016)

Question 4

satiety

Answer 4

Satiety: feeling full after eating, inhibiting intake between meals

Question 5

satiation

Answer 5

Satiation: within meal process determining when you stop eating

Question 6

expected satiety

Answer 6

• Expected satiety: perception, before consumption, of the ability of a food to stave off hunger

Question 7

expected satiation

Answer 7

• Expected satiation; perception, before consumption, of the ability of a food to deliver fullness

Question 8

what can expected satiety/satiation predict?

Answer 8

• Experimental evidence to suggest that expected satiation/satiety of foods can strongly influence pre-meal decisions about food and portion selection (e.g. Brunstrom, Shakeshaft & Alexander)

Question 9

what determines expected satiation/satiety?

Answer 9

• Can be learned
  ○ More familiar food, more filling it is expected to be (routines)
  
  • Influenced by perceived volume of food
    ○ Larger volume, more filling expected (volume)
  • Exposure to varieties of food reduces expected satiety/satiation (variety)
  • Energy density negatively correlated with expected satiety
    ○ Higher the foods energy density, less filling it is perceived to be (energy density)
  • Routine decisions and automatic processing can lead to passive overconsumption of foods.

Question 10

does portion size affect food intake?

Answer 10

• Rolls, Morris & Roe (2022)
  ○ 30% more energy for largest portions (1000g) compared to the smallest (500g)
  
  • Rolls et al., (2004)
    ○ Replicated with sandwiches
    ○ Gender differences
    ○ Similar ratings of fullness
  • Meta-analysis of 65 studies found that doubling the portion served to individuals, increases food intake by ~35% (Zlatevska, Dubelaar & Holden, 2014)
  • More pronounced in males

Question 11

what do larger portions do in terms of satiation/satiety?

Answer 11

○ Encourage consumption past satiation
○ Indicates socially appropriate amount to consume
○ Adjust biological signals and cognitive perceptions over time about what portion elicits satiety
○ Driven by primal instincts to consume as much food as possible when available

Question 12

why does portion size affect food intake?

Answer 12

• Ability to regulate food intake changes as we age - children <3 years old better at regulating intake and less affected by external cues
  
  • Experimental evidence indicates significant impact on food intake in the short term; similar effects in naturalistic settings
  • Longitudinally - limited adjustment for increases in intake (e.g., Rolls, 2006; Vermeer et al., 2011)
    ○ The upper end ‘set point’ intervention to reduce intake is much weaker than the lower end intervention to increase intake.

Question 13

are there individual differences in the portion size effect? evidence

Answer 13

• Cunningham et al., (2023).
  ○ Repeated measures over four weeks.
  ○ Macaroni cheese served in 400g to 700g portion sizes (increases by 100g)
  ○ N = 44 (29 female)
  ○ Explored how elements of eating microstructure (e.g., meal duration, bite count, mean bite size, and mean eating rate) were linked to portion size increases.
  ○ Faster eating rate and larger bite sizes were related to greater food consumption as larger portion sizes are served; but did not moderate the degree of increase in food intake across larger portions.
  ○ Serving larger portions, eating faster, and taking larger bits all combine to contribute to greater food intake.

Question 14

why do increased portion sizes lead to increased consumption?

Answer 14

• External cues
  
  • Physiological regulatory mechanisms overridden by learned behaviours

Question 15

why do we overconsume fat?

Answer 15

• Highly palatable: texture, flavour, cross-modal sensory effects

Question 16

satiety signals for fat consumption

Answer 16

○ Preload studies (early work): Pro > CHO > fat
○ Later work: similar effect of CHO and fat on subsequent intake of test meal when palatability and energy density matched

Question 17

energy density of fat

Answer 17

• Energy density of fat is high – 9kcal/g (4kcal/g CHO & protein). Small portions of fatty food can therefore have a high energy content.

Question 18

effects of satiation on fat consumption

Answer 18

○ Tendency to consume constant weight of food; regardless of
macronutrient content. E.g., Stubbs et al., 1996, Saltzman, 1997.
○ Therefore, we may overconsume fat due to its high energy density in comparison to other foods.
○ We are poor at recognising energy density of foods and adjusting intake.

Question 19

palatability of fats and their traceability

Answer 19

• Palatability of fats can be traced to our primal roots
  ○ Foods high in fat contribute the most (in energy) to satisfy our biological drive to have the necessary energy for survival.
  ○ We are highly motivated therefore to seek out foods high in fat, sugar, salt and energy density to ‘ensure our survival’.

Question 20

what is the most satiating macro?

Answer 20

Protein is most satiating and then carbs and fat are pretty similar next.

Question 21

passive overconsumption

Answer 21

• We tend to consume a constant weight of food, despite variations in macronutrient content
  
  • High energy density of highly liked, high-fat foods → overconsumption of fat
  • Fat has a relatively weak effect on satiation and satiety (relative to protein)
  • Passive overconsumption (high fat hyperphagia)

Question 22

Can we alter our predisposition to consume energy dense foods?

Answer 22

• Individual differences in self-control and in rewarding nature of food
  Food response inhibition training

Question 23

Lawrence et al., 2015. Appetite, 95(1) 17-28

Food response inhibition training task:

findings

Answer 23

1. Reduced liking of no-go food
   
   2. Reduced consumption of no-go
      food
   3. Less likely to choose the no-go
      food
   4. Reduced portion sizes of no-go food.
      - Preliminary evidence to suggest reduction in weight among trained group at 1 and 6 month follow up.
      - Jones et al., (2016) Meta-analysis. Robust evidence to suggest that participants exposed to inhibitory control training consume significantly less food/drink than control.

Question 24

what is appetite associated with?

Answer 24

• Appetite not just associated with hypothalamic control
  
  • Texture, flavour, cross-modal sensory experiences
  • Associated emotions and memory of foods are also important

Question 25

brain regions for appetite and eating?

Answer 25

○ PFC (planning and decision making)
○ Nucleus accumbens (pleasure and aversive taste memories)
○ Amygdala (memory)
○ VTA (dopamine reward system)
○ Parabrachial nucleus (release of pleasure based substances like endorphins)

Question 26

what is palatability?

Answer 26

• “Palatability is the hedonic component of food reward, and results from a central integrative process that can incorporate aspects not only of the taste, but of the physiological state and of the individual’s associative history” (Berridge, 1996).

Question 27

what are the 2 Hedonic (non-homeostatic) reward mechanisms

Answer 27

○ Affect (liking)
○ Motivation (wanting)

Question 28

what is liking measured through in studies? Berridge (2009)

Answer 28

pleasure responses (facial expressions) in animals and subjective ratings of pleasantness in humans

Question 29

what is wanting measured through in studies? Berridge (2009)

Answer 29

• Wanting is measured through incentive motivation (instrumental behaviour) in animals and desire to eat in humans.

Question 30

neuropsychology and responses of liking and wanting

Answer 30

• Berridge (1996): Lesion studies demonstrated liking & wanting activated different areas of the brain in animals

Question 31

evidence from pharmacological studies of liking and wanting

Answer 31

• Evidence from pharmacological studies in humans suggest activation of different systems and neurotransmitters.
  ○ Liking: – opioid and GABAnergic systems
  § Opioid blockers reduce pleasantness but not hunger (e.g., Cambridge et al., 2013; Drewnowski et al., 1995).
  ○ Wanting: – Dopaminergic neurotransmitters
  § Dexfenfluramine –reduce hunger but no effect on pleasantness (e.g.,
  Blundell & Hill, 1992)
  
  • Much more difficult to dissociate using self-report; poor awareness of hedonic changes

Question 32

dissociating liking and wanting

Answer 32

• Finlayson, King & Blundell (2007).
  ○ 53 participants; mean age 21.4
  ○ Photos of 20 foods (high fat, low fat, savoury, sweet)
  § Liking–Visual Analog Scale
  § Wanting – Forced choice
  “Which of these foods would you most like to eat now?”
  ○ Changes in food liking and wanting assessed pre & post meal.
  • When hungry…
    ○ Wanted high fat savoury over low fat savoury; no differences in liking.
    ○ Liked high fat sweet more than low fat sweet, but no differences in wanting.
  • When satiated, the pattern was reversed:
    ○ Liked high fat savoury over low fat savoury, but no differences in wanting
    ○ Wanted high fat sweet foods over low fat sweet foods, but no differences in liking

Question 33

evidence for the fact that - Increasing variety in taste, texture, appearance and choice of foods can increase food intake, and is linked with higher weight.

Answer 33

1. Pliner et al (1980) – different spreads on bread
   2. Bellisle & LeMagnen (1980) – Pizza, sausage rolls & egg
   roll (together or singularly)
   3. Rolls, van Duijvenvoorde & Rolls (1984) – Four different courses vs. four courses of the same food (40% increase)
   4. Wisniewski et al (1992) – Eat to satiety. Presented with the same or a different food. 3-fold increase in consumption of new food.

Question 34

evidence for sensory specific satiety

Answer 34

• (Rolls, 1986)
  ○ Changes in pleasantness occur rapidly (within 2 minutes of consumption) and last up to an hour (Hetherington, Burley, & Rolls, 1989).
  ○ The decrease in enjoyment and intake of the already-consumed food is driven by a reduction in both liking and wanting of the food (Brunstrom & Mitchell, 2006; Havermans et al., 2009; Raynor & Epstein, 2001).
  ○ Suggests that it occurs a result of sensory stimulation rather than postabsorbtive affects (largest changes occur before meal absorbed).
  ○ Important impact on meal termination (and overall intake). Variety undermines the process and promotes increased consumption.

Question 35

how specific is SSS?

Answer 35

• Greatest changes in palatability occur for the food eaten
  
  • Decreases in pleasantness of other foods may also occur, due to:
    ○ Similarity in sensory properties or flavour
    ○ Cognitively the same ‘type’ of food
    ○ Similarity in macronutrient content
    § E.g., sweet versus savoury foods; orange jelly & raspberry jelly
  • Intake increases with changes in sensory properties
    ○ E.g., flavour, shape, texture. Variation in pasta shapes→15% increase in intake over 3 courses

Question 36

what does variety do to SSS?

Answer 36

• Variety promotes switching between foods, which may delay SSS.

Question 37

impact of fluids on SSS

Answer 37

• Cunningham et al., (2023)
  ○ Video recordings of meal consumption
  ○ Assessed patterns of bites, sips and the number of
  switches between them; also assessed SSS
  
  • Switching between bites and sips more frequently was linked with greater food consumption
  • Overall water intake was also linked with greater food intake.
  • Suggestion that switching between food and water may promote energy intake by attenuating the development of SSS

Question 38

mechanisms of SSS

Answer 38

1. Habituation & monotony (Epstein et al, 1992; 1993)
   
   • Reduction in pleasantness of, & salivation to lemon juice over 10 trials;
     presentation of new stimulus dishabituated response
   • Pleasantness of water reduced among those who tasted it AND those
     who drank it (Rolls, 1982).
   • Habituation regardless of energy content or ingestion.
2. Central mechanisms - neurophysiological explanation (Rolls, 1993)
   
   • Satiety linked to decreased OFC neuronal response
3. A role for endogenous opioids
   
   • Hypothalamic release of opioid peptides associated with reward
   • Blocking the release or the reuptake of these peptides (via drugs) disrupts SSS

Question 39

the appetizer effect

Answer 39

• The Appetizer Effect (Yeomans, 1996)
  ○ High initial ratings of highly liked food
  ○ Offered bland, palatable and strong flavoured
  food (pasta + oregano).
  ○ Palatable flavour → enhanced intake, eating rate
  and reported appetite (the appetizer effect)
  ○ Decline in pleasantness & desire to eat still
  follows – reflects satiation
  ○ So, sensory stimulation explains initiation not termination

Question 40

what is hunger

Answer 40

• “The expression of hunger is actually grounded in an absence of fullness and it is this feeling that underlies readiness to eat”
  
  • BUT you can be ready to eat while being full (e.g., the dessert effect in SSS).
  • “Hunger reflects the readiness to eat in the absence of fullness and in anticipation of pleasure” (Rogers & Brunstrom, 2016).