Hedonistic Eating Flashcards
Set point assumptions
Body’s energy resource are maintained at an optimal level
Hunger and satiety
Not normally to eat by energy deficit but anticipation of hunger as it is evolutionary adaptive
Pavlovs dog
Indicates that hunger is not triggered by just energy deficit as at any stage of hunger the dog would salivate
This is an indication that motivation to eat was triggered by the anticipation of food
Many studies show environmental cues can initiate eating
America Samoa a tiny island has 75% obesity - due to recent western diet (The Lancet 2015)
Bundred 2001
Boys over weight has increased to nearly a third between 1988 and 1998
Genetic
Obesity has increased too rapidly to be due to genetic factors
Twin studies do show a heritability factor
But it’s so rapid that the environment and lifestyle changes must be key
Genes do not cause obesity but predispose the risk of becoming obese
Berthoud 2004; Friedman 2003
Fraction of the population genetically prone to environmental push to obesity and thirst resistant
Evolutionary explanations
Food cane as high physical cost (hunting) and worrying about excess energy wasn’t a thing
‘Thrifty gene’ - genes that allowed the procurement of food, made efficient use of ingested calories - fat storage
Obesity now occurs as physical cost of food is low
Was good to over eat high energy food as it kept them going through famine this could explain why we prefer high calorie foods
Opportunist eating - eat whenever food was available
Selective attention mechanisms mean we tend to have a bias towards foods
Limited storage capacity - fat storage
These were adaptive, the environment now is very different - acceable foods, less activity, increasing portion sizes (soda is 6x), advertising
Hedonic hunger
Lowe and Butryn 2007
Food consumption driven by pleasure
Availability of food may be creating the psychological effects of other hedonic driven activities (drugs) - very easy to over consume and think about food
There are different brain mechanisms that control it than to homeostatic eating
Dieting is hard because it involves eating less than wanted not needed
Appetiser effect
Consumption of tasty food increases hunger early in the meal relative to bland or strong flavoured food
Yeomans 1996
This makes no sense homeostaticly as food should decrease hunger
Sensory specific satiety
Decline in pleasantness and reward value of food as it is being eaten relative to uneaten foods
O’Doherty 2000
Pleasantness ratings of banana odour decreased after eating bananas however pleasantness of vanilla did not change
Activation of OFC decreased to the banana odour but not vanilla
Homeostatic
Beethoud 2004
Homeostatic control is asymmetrical- low body weight is defended
Eat more command is dominant
Was adaptive but now counter productive (Zhang 2009)
Berthoud 2004
St and Lt signals party of the homeostatic system influence eating behaviours
Cognitive and environmental factors are part of hedonistic and the power of pleasure overwhelms the homeostatic system
Rewards
Something desired because it produces pleasure
May influence behaviour in the absence of being consciously aware (Berridge 2009)
Food reward is momentary value at the time of ingestion (Rogers 2015)
Learning
Cortico limbic neural network is involved in learning and maintaining representations of predictive food related rewards (Gottfried 2003)
The amygdala and OFC are activated in response to visual conditioned stimuli as part of learning picture odour associations in Hungry pps when the meal is eaten activity and hunger decreases - but not for a different stimuli (sensory specific satiety)
Critic limbic system important for encoding predictive reward related value of cues
Reward of dopamine
Nice self administered intracranial electrical stimulation - must feel good
Stimulation of forebrain bundle has dopamine releasing neurones travelling from VTA to NAcc - firing of neurones associated with reward
Dopamine containing neurones modulate the outcome of brain stimulation - dopamine involved in reward
Dopamine increasing drugs (amphetamines) enhance reward effect of electrical stimulation in rats
Dopamine receptor antagonists (block) reduce brain stimulation
Anhedonia theory
Dopamine mediates pleasure
Disruption causes aphagia ( failure to eat)
Dopamine receptors antagonists reduce motivation to work for food
Loss of motivation due to loss of reward - hedonic consequence
- dopamine blockade prevents animals from attending food and working, reflects a motor incapacity
- stimulation of dopamine does not increase eating
- dopamine is not needed to feel pleasure from eating
Berridge theory
Replaced anhedina
Reward contains distinguishable psychological components that are controlled by separate neurobiological systems
Distinction between affective and motivational consequences of consuming food
Finlayson 2006 ; Berridge 2010
Wanting and liking are separate but interlinked components of reward control motivated behaviour
Wanting = anticipation
Liking = pleasure
Dopamine
Chemical lesions of dopamine systems results in aphagia (not eating) but still have normal taste reactivity ( still like food if no dopamine)
Plays a role in recognition of motivationally important stimuli, energising goal directed behaviour and learning associations
This related to wanting
Promotes expenditure of effort in tasks
Low dopamine rats settle for less food - don’t make effort to climb barrier
Concluded that accumbens domapine promotes effort
Opiates
Mediate liking
Morphine bind to receptors suggesting opiate like chemicals occur naturally
Endorphins (endogenous opioids)
Increase food intake and opioid antagonists such as naloxone, reduce intake
Experiments show a role for liking not wanting
Kirkham and cooper (1998)
Sham fed rats - psychological and physiological processes were separated
Opioid receptors blockade by naloxone reduces the reward associated with sweet taste
Drewnowski
Humans have a reduced hedonic preferences for sugar and fat
Reduces palatable food intake in people
Strong effect of reducing caloric intake for sweet and high fat food, no effect on non sweet food
Perception of sweetness or fat was unchanged and hunger and fullness ratings were not effected
Opioid receptor agonists increase likining - sites in NAcc are sensitive
Taste reaction tests show these sites support opioid mediating liking
Eating palatable food releases opioid la here
Wanting and memory
A mental representation of pleasure and anticipation is learn through memory
The value of the reward determines the power of it to attract and modulates motivation
Wanting drives us to obtain food, liking makes sure we eat it - no matter how much we wanted it if it’s horrible we won’t eat it
Hedonic everlasting is critical
Obese vs lean
Wanting and liking
Obese people are thought to have a weakened satiety response
Evidence that biological systems are intact but overridden by hedonic stimulation (Berthoud 2004)
Little evidence that they like food more. (Cox 1999)
Mela 2006
May be associates with a greater motivation for food but without deriving any great pleasure from the orosensory experience
So individual difference in responsiveness to foods related cues may be critical
Saelenst 1996
Complete computer task (work) to gain food points. Food reinforcement changed across tasks and they found obese pps work harder to obtain food
Craving is wanting and during fMRI choco-cravers showed greater activation in the medial OFC and ventricular striatum than on cravers
These are sites in the reward network suggesting it’s salient
Obese vs Lean
Cue reactivity
Ferriday (2011)
Exposure to pizza increased desire to eat and salivary response in over weight relative to lean
Increased cue reactivity in obese people shows an enhance motivation to food
Castellanos (2009)
Obese pps have a greater attention bias when tested in fasted and fed conditions - once fed bias if lean decreases
Rothemund (2007) m
FMRI study, pps looking at high calorie food, utensils and low cal food after not eating for 1.5 hours
Obese individuals showed greater activation to high cal than neutral in key areas associated with reward and motivation and in the hippocampus (memory)
Obese vs Lean
Cue
Carbell 2012
Review that obesity is associated with heightened or abnormal responses to cues in brain regions associated with reward motivation memory and emotion
Heightened activation in areas of cognitive control which are greater in fasted state
Yokum 2011
Cause or consequences
Examine food cues in fMRI
Initial attentions bias and bmi were positively correlated with activation of areas of reward
Greater OFC activation to appetising food predicted increased bmi
Implications
Exeter uni
Pps play a game that has you avoid unhealthy foods pps did lose a bit of weight and stopped eating sugary foods and fat up to 6mths after
Nudging = small changes
Change he environment by reducing portions, limiting marketing, nutritional info
We have evolved efficient motivational mechanisms that direct us to food and encourage over consumption and permit storage of excess energy as an adaptation to food shortage
High obesity shows the efficiency of then
