Chapter 10 - The Motivation of Hunger and Eating Flashcards
(29 cards)
do stomach contractions cause hunger?
no. early theories (e.g., Cannon & Washburn 1912) linked stomach contractions to hunger, but later studies showed that people who had their stomachs surgically removed still feel hunger.
conclusion: stomach contractions accompany hunger, but do not cause it.
which part of the brain is primarily involved in hunger regulation?
the hypothalamus.
-early studies suggested that the lateral and ventromedial hypothalamus acted as on/off switches.
-modern research shows that hunger is regulated by complex neural circuits involving the arcuate and paraventricular nuclei, which are sensitive to both hunger and satiety signals.
digestive regulation of hunger
after eating, the stomach stretches, sending satiety signals to the brain via the vagus nerve.
*additional signals are sent along other nerves based on nutrient content.
hormonal regulation of hunger
-ghrelin (from stomach): stimulates hunger
-CCK (from upper intestine): signals satiety
-leptin (from fat cells): regulates long-term hunger; low leptin = more hunger
-insulin (from pancreas): sensitive to fat stores and influences hunger
*these hormones influence the hypothalamus, especially the arcuate and paraventricular nuclei
what three systems contribute to hunger regulation?
1 - brain regulation (hypothalamus)
2 - digestive signals (stomach stretch, nutrient content)
3 - hormonal regulation ( ghrelin, CCK, leptin, insulin)
the three key environmental factors of hunger regulation:
1 - the availability of food
2 - learned preferences or habits
3 - stress
palatability
the better food tastes, the more of it people and animals tend to consume
quantity available
people tend to eat more when more food is available or served; larger portions and larger plates can increase consumption
variety & sensory-specific satiety
humans and animals increase their consumption when a greater variety of foods is available.
sensory-specific satiety phenomenon: as you eat a specific food, its incentive value declines.
**if only a few foods are available, the appeal of all of them can decline quickly. but if many foods are available, people can keep shifting to new foods and end up eating more overall (e.g., buffets).
presence of others
on average, people eat 44% more when they eat with others as opposed to eating alone. the more people present, the more people tend to eat.
*when two people eat together they tend to use each other as guides and eat similar amounts.
*when women eat in the presence of a man they do not know well, they tend to reduce their intake.
stress
roughly 40-50% of people increase their food consumption in times of stress, and in many people, stress also fosters a shift toward less healthy food choices.
**note: stress has varied effects on eating, as it causes some individuals to eat less.
what kinds of environmental cues can trigger eating?
ads, smells, images, or videos of food can stimulate hunger and increase consumption.
what is the inhibitory norm model of social influence on eating?
Herman and Polivy’s theory that suggests that the presence of others generally inhibits eating. but, under certain specific conditions, eating may increase.
*in essence, they suggest that our eating is influenced by social norms determined by the behaviour of the others around us at the time.
learned preferences and habits
-while some food preferences are biological (e.g., sweet, fatty, salty), most are learned through experience and culture.
-food preferences are learned through classical conditioning, exposure, and cultural or social influences.
-repeated exposure to a food increases liking; children are more likely to try unfamiliar foods if an adult tries them first.
*note: forcing children to eat a certain food often backfires and can decrease liking.
define obesity
obesity is the condition of being overweight.
body mass index (BMI)
obesity is typically assessed using the BMI - weight (in kg) divided by height (in metres) squared. (kg/m^2).
a BMI of 25.0-29.9 is typically considered overweight, and a BMI over 30 is generally considered obese.
according to Statistics Canada (2015e) what percentage of Canadian adults were obese?
20.2% of Canadians over 18 were classified as obese.
Which Canadian provinces had the lowest obesity rates?
Quebec and BC
Which regions had the highest obesity rates?
-North West territories
-Newfoundland and Labrador
-New Brunswick
-Nunavut
-PEI
-Nova Scotia
-Saskatchewan
-Manitoba
How many Canadian children are classified as obese?
about 1 in 7
How has global obesity changed since 1975 according to the World Health Organization (WHO)?
obesity rates have triples; 39% of the world is overweight and 13% is obese.
what evolutionary explanation is given for the rise in obesity?
humans evolved to overeat when food was available due to food scarcity in the past; today’s food abundance leads to chronic overeating.
What health risks are increased by obesity?
coronary disease, stroke, diabetes, hypertension, arthritis, sleep apnea, some cancers, and possibly Alzheimer’s.
what role do genetics play in obesity?
twin studies suggest that genetics account for 61% of weight variation in men and 73% in women.
