Lecture 9. Hunger, Eating, and Health Flashcards
a behavior that is of interest to virtually everyone and most of us derive great pleasure from it
eating
Eating too much is associated with
eating-related health problems
The average American consumes ___ calories per day, about twice the average daily requirement.
3,800
motivation to eat
hunger
main purpose of hunger
increase the probability of eating
eating’s main purpose:
to supply the body with the molecular building blocks and energy it needs to survive and function
the gastrointestinal process of breaking down food and absorbing its constituents into the body
Digestion
Much of the work of breaking down the food we ingest is done by the constituents of our ________
gut microbiome
process of digestion that breaks up food and mixes it with saliva
Chewing
process in digestion that lubricates food and begins its digestion.
saliva
process in digestion that moves food and drink down the esophagus to the stomach.
swallowing
The primary function of the stomach is
to serve as a storage reservoir
process in digestion that breaks food down into small particles
hydrochloric acid in the stomach
during digestion process, this begins the process of breaking down protein molecules to amino acids.
pepsin
The stomach gradually empties its contents through the ____ into the duodenum
pyloric sphincter
the upper portion of the intestine, where most of the absorption takes place.
duodenum
many of them from the gallbladder and pancreas, break down protein molecules to amino acids, and starch and complex sugar molecules to simple sugars
Digestive enzymes in the duodenum
Fats are emulsified by
bile
Energy is Delivered to the Body in 3 Forms
- lipids
- amino acids
- glucose
Energy is Stored In the Body in 3 Forms
- fats
- protein
- glycogen
the breakdown products of
proteins
amino acids
a simple sugar that is a breakdown product of complex carbohydrates
Glucose
preferred mode of energy
storage
fats
most of the body’s _____ are stored as fats
energy reserves
chemical changes by which energy is made available for an organism’s use
energy metabolism
3 Phases of Energy Metabolism
- Cephalic Phase
- Absorptive Phase
- Fasting Phase
Phase of energy metabolism that begins with the sight, smell, or even the thought of food, and it ends when the food starts to be absorbed into the bloodstream
cephalic phase
period during which the energy absorbed into the bloodstream from the meal is meeting the body’s immediate energy needs
absorptive phase
period during which all of the unstored energy from the previous meal has been used and the body is withdrawing energy from its reserves to meet its energy requirements
fasting phase
Flow during the 3 Phases is controlled by 2 pancreatic hormones
- insulin
- glucagon
insulin’s 3 functions
- promotes the use of glucose as the primary source of energy by the body
- promotes the conversion of bloodborne fuels that can be stored
- promotes the storage of glycogen in liver and muscle, fat in adipose tissue, and proteins in muscle
In cephalic and absorptive phase, there is ___ insulin, ___ glucagon
high, low
In fasting phase, there is ___ insulin, ___ glucagon
low, high
promote the conversion of glycogen and protein to glucose
gluconeogenesis
high levels of fasting-phase glucagon promote the ____
release of free fatty acids from adipose tissue and their use as the body’s primary fuel
used by muscles as a source of energy during the fasting phase
ketones
Theories of Hunger and Eating
Set Points and Positive Incentives
Set-point assumption is aka
set-point model or set-point system
belief that hunger and eating are normally triggered when the body’s energy resources fall below a prescribed optimal level, or set point
Set-point assumption
3 components of set-point assumption
- set-point mechanism
- detector mechanism
- effector mechanism
defines the set point
set-point mechanism
detects deviations from the set point
detector mechanism
acts to eliminate the deviations
effector mechanism
systems in which feedback from changes in one direction elicit compensatory effects in the opposite directions
Negative Feedback Systems
The dominant view in the 1950s was that eating is self-regulated by the interaction between two set-point systems:
- a short-term glucostatic system
- a long-term lipostatic system
account for meal initiation and termination
Glucostatic Theory
account for long-term regulation and support how body weights of adults stay relatively constant
lipostatic theory
determine when we eat
glucose levels
determine how much we eat over long-term
fat stores
alternative theoretical perspective
Positive-incentive perspective
anticipated pleasure of a behavior
positive-incentive value
humans and other animals are not normally driven to eat by internal energy deficits but are drawn to eat by the anticipated pleasure of eating
Positive-Incentive Theory
Factors that Determine What we Eat
- Learned Taste Preference and Aversions
- Learning to Eat Vitamins and Minerals
Factors that Determine When we Eat
- Premeal Hunger
- Pavlovian Condition of Hunger
Factors that Determine How much we Eat
- Satiety Signals
- Sham Eating
- Appetizer Effect and Satiety
- Serving Sizes and Satiety
- Social Influences and Satiety
- Sensory Specific Satiety
feeling that motivates us to stop eating a meal when there is still food left
satiety
satiety signals depend on
both the volume and nutritive density (calories per unit volume) of the food.
Satiety signals, which make us stop eating, can be induced by
food in the gut and glucose in the blood
Four observations supporting the view that intention to eat causes the drop in blood glucose
- the rapid timing of the glucose drop
- the persistence of eating without the drop
- the return of blood glucose to normal
when an expected meal isn’t served, - relatively stable glucose levels in the fluid around brain neurons.
In the 1950s, research on rats suggested that the hypothalamus controlled eating behavior, with the ____ and ____
- ventromedial hypothalamus (VMH)
- lateral hypothalamus (LH)
In the myth of Hypothalamic Hunger and Satiety Centers, this is thought to regulate satiety
ventromedial hypothalamus (VMH)
In the myth of Hypothalamic Hunger and Satiety Centers, this is thought to control feeding
lateral hypothalamus (LH)
Early experiments found that VMH lesions led to ______
- hyperphagia
- obesity
LH lesions caused
- aphagia
- adipsia
excessive eating
hyperphagia
complete cessation of eating
aphagia
cessation of drinking
adipsia
Some further research observed that rats with VMH lesions gained weight because of
increased fat production and decreased fat
breakdown, leading to overeating to meet energy needs
Some further research observed that rats with LH lesions produced
various
motor disturbances and a lack of
responsiveness to sensory input,
indicating that the LH is not solely responsible for hunger
In Modern Research on the Role of Hypothalamic Nuclei in Hunger and Society, Certain neurons in the paraventricular nucleus of the hypothalamus and distinct neuronal populations in the arcuate nucleus have been identified as
nutrient sensors and regulators of metabolism
critical hub in a neural network that communicates with receptors in the blood and gut, suggesting a complex interplay in the regulation of feeding behavior
arcuate nucleus
They conducted a pioneering study where one of them swallowed a balloon connected to a tube, and the stomach contractions caused by hunger were recorded
Cannon and Washburn
Experiments suggested that the gastrointestinal tract is a source of
satiety signal
one of the first gut peptides discovered to reduce food intake when injected into hungry rats
Cholecystokinin (CCK)
provide information to the brain about the quantity and nature of food in the gastrointestinal tract
gut peptides
Research on gut peptides and hypothalamic circuits has highlighted the _____
gut’s role
monoaminergic neurotransmitter, has been found to play a role in metabolism and eating behavior
Serotonin
serotonin-induced satiety
- resistance to highly palatable diets
- a reduction in the amount of food consumed per meal
- a shift in food preferences away from fatty foods
a condition associated with excessive hunger and overeating
Prader-Willi Syndrome
prader-willi syndrome is characterized by
- weak muscles
- small hands and feet
- feeding problems in infancy behavioral issues like tantrums and compulsive behavior as well as skin
picking.
aim to prevent significant weight changes in adults
Set-point mechanisms
Set-point theories suggest each person’s set point is
optimal for their health
Caloric restriction can have positive effects on neurological conditions such as
- reducing seizures
- improving memory
The body controls its fat levels largely by
changing energy efficiency
As body fat decreases, energy usage becomes
more efficient, limiting further weight loss
weight gain leads to
decreased energy efficiency
is the mechanism behind energy efficiency adjustments based on
body fat levels.
Diet-induced thermogenesis
proposes that body weight naturally settles around an equilibrium influenced by various factors
settling point model
used to illustrate the settling-point mechanism
Leaky-barrel analogy
Causes of overeating
- evolutionary perspective
- cultural practices and beliefs
- parental influence
- modern environment
factors if why do some people gain weight from overeating while others do not?
1) differences in energy expenditure
2) differences in gut microbiome composition
3) genetic and epigenetic factors
4 differences in energy expenditure
- exercise
- basal metabolic rate
- diet-induced thermogenesis
- non-exercise activity thermogenesis (NEAT)
The gut microbiome outnumbers our own
bodily cells by
10 to 1
4 factors of ineffective weight loss programs
- typical weight loss programs
- difficulty of permanent lifestyle change
- efficiency of the body
- compensatory eating
a peptide hormone released from adipose tissue and encoded by the obese (ob) gene
leptin
treatment of overeating and high body-fat levels
- serotonergic agonists
- gastric Bypass Surgery
potential to reduce food consumption in both humans and animals, enhance short-term satiety signals associated with meal consumption and can reduce various overeating-related factors
serotonergic agonists
examples of serotonergic agonists
- fenfluramine and dexfenfluramine
- lorcaserin
a surgical treatment for those who are extremely overweight that involves short-circuiting the normal path of food through the digestive tract
gastric bypass surgery
involves surgically positioning a hollow silicone band around the stomach to reduce the flow of food through it.
Adjustable Gastric Band Procedure
characterized by a refusal to eat enough to maintain a healthy body weight
anorexia nervosa
characterized by periods of not eating interrupted by bingeing followed by efforts to immediately eliminate the consumed calories from the body by purging
bulimia nervosa
