cognition and appetite

Question 1

psychobiology view of appetite

Answer 1

• Eating is a consequence of physiological processes monitoring nutrient status.
  
  • But such models cannot explain…
  • Overeating and the rise in obesity
  • Many eating disorders
• Etc

Question 2

cognitive processes implicated in eating

Answer 2

· Attention:
- Responsiveness to food cues
- Awareness of physiological appetite signals
- Distraction while eating
· Memory:
- For food recently eaten
- For food liking
· Perception:
- Taste/smell
- Food liking
- Portion size
· Learning:
- Learned liking of food
- Expectations about how filling a food will be
· Decision making:
- About when to eat
- What to eat
- Healthy choices

Question 3

cognitive theories of susceptibility to overeat

Answer 3

· Externality theory - Susceptibility to weight gain is dependent on the
extent to which internal and external signals motivate a person to eat (Schachter 1968). Predicted that obese people would be more
responsive to external signals rather than physiological (internal) appetite signals.
· Restraint theory - Individuals use cognitive processes to restrict their
intake as a consequence of weight concerns. This cognitive restriction of food intake is predicted to lead to overeating when dietary restraint breaks down. The Three Factor Eating Questionnaire (Stunkard 1985) measures restrained eating.
- Emotional eating - Emotional eating occurs in response to negative emotions in an attempt to distract attention from, or alleviate, these feelings.

Question 4

measuring food-related attention - foot dot-probe task

Answer 4

· Paired stimuli - one food-related, one control, displayed for fixed time
· Neutral “dot” probe may appear in either location immediately after visual cues
· Measure in Reaction Time (RT) to probe.
- Attentional bias for food cues: faster reaction time (RT) when probe and food cue are in same location but slower RT when locations differ.

Question 5

measuring food related attention - food stroop task

Answer 5

Attentional bias for food cues: slower colour-naming time for food-related items compared with neutral stimuli.

Question 6

Attentional bias for food-related cues have been found in obese adults (e.g., Nijs et al, 2010; Werthmann, 2011, Dekuchi, 2017) and obese children (Braet and Crombez, 2003; Yokum et al, 2011).

Question 7

food attentional biases - state of play

Answer 7

1. Nearly 30 studies on biases in obese/overweight. Meta-analyses reliably confirm no evidence of greater attention in obesity.
   
   2. Food-related biases are reliably associated with:
      A) A) hunger state
      B) Food intake
      C) Food craving
      D) Certain eating disorders

Question 8

possible implications for appetite control

Answer 8

1) Inattention while eating could promote overconsumption (so-called “mindless eating”)
2) Inattention between meals may lead to poor awareness of interoceptive (i.e, bodily cues) relating to appetite

Question 9

inattention while eating

Answer 9

• Eating while distracted (e.g., TV watching) consistently leads to greater intake, and poorer memory of what was consumed (Robinson et al, 2013)
  
  • Obese children on average spend more time in sedentary behaviours and high TV viewing associated with higher intake (e.g., Crespo et al, 2001)
• Time watching TV associated with average 1.3x obesity risk in children (Ghobadi et al, 2018)

Question 10

reducing eating by modifying attention?

Answer 10

• Mindfulness:
  1) Attending to food during meals should lead to better control of intake.
  2) Training awareness of appetite sensations should lead to better appetite control.

Question 11

learning influences food liking

Answer 11

• We are born with an innate liking for sweet, disliking for bitter. All other flavour preferences are learnt.
  
  • Flavour preferences established in childhood will track into adulthood.
  • Therefore encouraging healthy eating habits in early life is very important for the prevention of adulthood obesity.
• Prenatal flavour learning (Mennella et al, 1995).

Question 12

expectations influence food liking

Answer 12

• Expectations about sensory qualities of a food can alter liking and perceptions of a food:
  
  • Assimilation theory:
  • The expected and sense sensory experience combine so that the actual evaluation of the food is closer to the expectations than is seen when the food is evaluated without any prior expectations
  • Soup label study
  • Yeomans, Lartamo, Procter, Lee, and Gray, 2001
    · Contrast effect:
  • Occurs when the expected and sensed sensory experience are very different resulting in a decrease in the rated quality of the food.
  • Smoked salmon ice cream study
• Yeomans, Chambers, Blumenthal, and Blake, 2008

Question 13

variety influences how liking changes

Answer 13

· Sensory specific satiety (SSS) - decrease in palatability of recently eaten food - decrease in desire for a food just eaten while still desiring more of other foods. For example, having enough of a main course but still having an appetite for dessert.
- Decrease in palatability is because of habituation to sensory properties of the eaten food.

Question 14

sensory-specific satiety and obesity

Answer 14

· Role in obesity?:
· Evidence that obese people show no within meal decrease in palatability for eaten foods while also desiring other foods.
- Obesegenic environment which is full of different types of food keeps renewing desire for food.

Question 15

decision making - portion size selection

Answer 15

· Plate cleaning occurs in 91% if meals (Fay et al, 2011)
· Thus decisions about how much we serve ourselves are important
· What do people base these portions size decisions on?

Question 16

increasing portion size makes us eat more?

Answer 16

· Many studies show that increasing portion-size increases intake, in some cases by 70-80%
· Visual cues are important: e.g. participants ate soup from a bowl with a hidden supply tube either with self-filling, static or self-emptying conditions.
- How full they felt 2 and 3h later was more influenced by what they thought they had consumed than actual consumption (Brunstrom et al. 2012)

Question 17

modifying perceptions to reduce obesity

Answer 17

· Establish healthy eating in childhood (learnt liking)
· Change eating environment (e.g., plate size)
· Increase expectations that foods will be filling so small portions are selected
· Regulate advertising high fat high sugar foods? (assimilation effect)
· Decrease variety (sensory specific satiety)
- Make all food taste the same (sensory specific satiety)?!

Question 18

memory and eating - healthy participants

Answer 18

· Is the memory of a recent meal an important influence on how much is consumed at the next eating episode?
- Series of studies by Higss et al using healthy participants e.g.,:
· These studies indicate that thinking about recently eaten food reduces intake at the next eating episode.
- These memory manipulations did not influence food liking.

Question 19

memory and overeating

Answer 19

• Disrupting encoding of memories while eating results in overeating at the next meal
  · Sedentary activities such as TV viewing are associated with obesity. It is assumed that this is because of reduced energy expenditure, however:
  
  • “Preschool children who watch more TV are fatter and are less active. However, despite TV viewing being linked to lower physical activity, the relation between TV viewing and fatness is not mediated by physical activity. The results suggest that a relation between TV viewing and fatness is more likely to be due to an effect on food intake.” (AJCN: Jackson et , 2009)
    · Perhaps disruption of memory encoding contributes to the relationship between TV watching
    and obesity?

Question 20

reducing intake by enhancing memories?

Answer 20

· Obesity interventions applying these findings might:
· Aim to enhance meal memories by:
- Increasing attention to experience of eating
- Slowing down eating rate
- Discouraging distractions while eating

Question 21

summary

Answer 21

· Cognitive processes influence:
· When we initiate a meal:
- Attentional bias for food cues when hungry
· How much we put on our plate:
- Expectations about fillingness of food
- Perception of portion size
· How much we like a food:
- Early life experiences
- Expectations of taste
- Variety of food available
· How much we eat at the next meal:
- Memory of recent eating
· These appetite-related cognitive processes may contribute to overeating and obesity
- These processes can be targeted for the prevention and treatment of overeating and obesity.