PSYC104 Lecture Notes - Lecture 3: Leader Board, Ghrelin, Binge Eating Disorder
30 May 2018
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PSYC104
WEEK 3 LECTURE
Why do scientists study eating?
- Big impact on your health (and pocket)
• By 2025 – 1 in 3 Australian adults will be obese
• Many will develop obesity -related diseases
• Poor quality diet linked to cancer and heart disease
• Eating disorders – costly and hard to treat – Anorexia is the deadliest of all psychiatric
conditions
• Diet – related illness costs our health system about $60 billion/year
- Eating is big business in Australia
• Processed food manufacture has a turnover of around $74 billion/year
• Fast food sales alone = $17billion/ year
• Food and liquor = 46% of retail spending = $112 billion/year
• Food exports = $30 billion/year = 11% of our total exports
How do we control food intake?
- Body
• Internal forces – Biological factors
➢ Energy levels
➢ Sensation – when eating and drinking
➢ Digestive system – stimulating us in eating or stopping
- Brain
• Biological and psychological
➢ Neurochemicals and brain structures
➢ Conscious/ unconscious – processes and engagement
- Environment
• External factors
➢ Food
➢ Time and place
➢ People and leisure
➢ Portion and plate
Body – Energy Levels
- The body has two modes of energy storage
• Short term – uses glucose; less important for intake – most powerful to regulate the
appetite
➢ Glucose goes up = Full
➢ Glucose goes down = Hungry
• Long term – uses fat; more important for intake
- Changes in body fat affect appetite
• Fat cells secrete a hormone called leptin
• More fat = more leptin – suppress appetite
• Less fat = less leptin – allowing food intake to increase
find more resources at oneclass.com
find more resources at oneclass.com
PSYC104
WEEK 3 LECTURE
Body – Sensation
- Food flavour drives intake
• Taste, smell and touch form flavour
• Hard-wired to like sweet, salty and fatty things
• Assoiated ith the foods appeaae ad sell
• When we see/smell nice food we want to eat it
- Sensory specific satiety slows intake in a meal
• The more we eat of a specific food, the more our liking for it declines
➢ Acts to signal the end of a meal (before stomach and gut signals tell your
brain you are full)
➢ It also drives dietary variety
Body – Digestive organs
- Multiple systems are involved in digesting food and all send signals to the brain about their
status
- Some of the signals
• Stomach is distended or empty
• Gut and stomach taste receptors
• Stomach is emptying its nutrient rich content (chyme) into the small intestine
• Gut bacterial signals of fat content
- Signals communicated to the brain
• Nerves (e.g Vagus)
• Hormones (e.g CCK and ghrelin)
• Nutrients (e.g. blood lipoproteins)
- Gut has a mini-brain: 500 million neurons
- Roughly as complex as the entire nervous system of the domestic cat
Brain – Neurochemicals
- Many neurochemicals modulate eating
- Two important examples are serotonin (SE) and dopamine (DA)
• Increased levels of both suppress appetite
➢ Most commercial appetite suppressants are SE or DA agonists (i.e., these drugs bind
to SE or DA receptors)
➢ Many common psychiatric drugs affect these neurotransmitters, and so many also
affect body weight
- Neurochemicals are modulated by events in the body
• Leptin (from fat cells) stimulates release of CRH in the brain (corticotrophin releasing
hormone) suppressing appetite
• Grehlin (from stomach) stimulates release of NY (Neuropeptide Y) in the brain increasing
appetite
find more resources at oneclass.com
find more resources at oneclass.com
PSYC104
WEEK 3 LECTURE
Brain – Locations
- Hypothalamus (lesions, imaging)
• Ventromedial nucleus (stop eating)
• Lateral hypothalamus (start eating)
• CRH and NY exert their effects here
- Cortical (lesions, imaging)
• Frontal (impulsivity)
• Insula (interception)
- Limbic system (lesions, imaging)
• Hippocampus (memory)
➢ Eating and HM
Environment – Food
- A potent means of getting you eat is to show food
• If you like it, this will trigger a desire to eat and a cephalic phase response (salivation,
insulin release etc)
- All of this is pretty sensible from an evolutionary perspective, because in the past if you
ae aoss good food it ould e e sesile to eat it
- Hoee, e at o esape from palatable food
• Everywhere there are snack machines, coffee shops, delis and supermarkets all packed
with delicious food
• There are few social prohibitions on eating – anywhere and anytime is fine
• Food advertising is ubiquitous
➢ In the US 4.2 billion dollars is spent per year advertising just fast food
Environment – Time and place
- People can be quite habit bound
• They often tend to eat at the same time and place each day
• Time of day and place then become associated with eating
• These can then become cues to trigger hunger and eating
➢ You can see this clearing when you travel across multiple time zones and you get
hungry at inappropriate times
- When people are placed in deep caves, with no cues to the passage of time, eating
behaviour changes significantly
• The size of the last meal then dictates how long it will be before the next meal – not the
time on the clock
Environment – People and leisure
- One of the most potent effects on how much we eat is the number of people we eat with
• These effects occur for all meal types
• They occur with family, friends, partners and even strangers
• They also occur in animals
- Another important appetite stimulant is TV
• TV is the principal leisure activity of most Westerners
• Eating with TV can stimulate eating in several ways
• Adverts, learning and distraction- to name a few
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Digestive system stimulating us in eating or stopping. The body has two modes of energy storage: short term uses glucose; less important for intake most powerful to regulate the appetite. Long term uses fat; more important for intake. Changes in body fat affect appetite: fat cells secrete a hormone called leptin, more fat = more leptin suppress appetite. Less fat = less leptin allowing food intake to increase. Food flavour drives intake: taste, smell and touch form flavour, hard-wired to like sweet, salty and fatty things, asso(cid:272)iated (cid:449)ith the food(cid:859)s appea(cid:396)a(cid:374)(cid:272)e a(cid:374)d s(cid:373)ell, when we see/smell nice food we want to eat it. Sensory specific satiety slows intake in a meal: the more we eat of a specific food, the more our liking for it declines. Acts to signal the end of a meal (before stomach and gut signals tell your brain you are full)
