module 4 Flashcards
how many calories does the avg American consume per day?
how many times required is this?
3800, 2x
what percentage of the US population is overweight or obese?
68
what is the lifetime prevalence of individuals in the US with anorexia or bulimia
1.2
what is the common assumption about the trigger for eating?
when the bodies energy sources fall below a set point
Describe the case of the “man who forgot not to eat”
RH was offered 4 meals at 15 minute intervals, ate the first three no problem, didn’t eat the fourth, then after a few minutes went for a walk to get more
what is the primary purpose of hunger?
what is the primary purpose of eating?
- to increase probability of eating
2. to supply the body with molecular building blocks
define digestion
gastrointenstinal process of breaking down food and absorbing its constituents into the body
what is the gut biome, and what is its main function?
the bacteria and other organisms living within our gastrointestinal tract.
to breakdown food as it passes through the tract
what are the three forms of stored energy in the body, and why are they necc?
- fats, glycogen and proteins
2. bc the body continuously uses energy but does not continuously absorb it
what is the bodies preferred storage system?
why? as related to glycogen (2)?
fats
- store around 2x as much energy per gram as glyc
- does nt hold a lot of water (if we stored mostly as glycogen, we would be fuckin heavy)
what are the three phases of energy metabolism
- cephalic phase
- absorptive
- fasting
describe the cephalic phase of enrg meta
- prepratory phase, begins with the perception of food and ends with the food beginning to be absorbed
describe the absorptive phase of enrg meta
- energy absorbed from a meal is meeting to bodies immediate energy needs
describe the fasting phase of enrg meta
all of the unstirred enrg from the previous meal has been used, and the body is now using enrg from its reserves
- ends at the beginning of the next cephalic
what does the process of energy metabolism look like in those who are gaining weight rapidly?
cut out the fasting phase, straight from cephalic to absorption
what are the two hormones that control the stages f energy metabolism?
where are they secreted?
- insulin
- glucagon
- - pancreas
during which phases does the body release insulin > glucagon?
cephalic and absorptive
what are the three main functions of insulin?
- promotes the use of glucose as the primary energy source
- promotes the conversion f blood borne fuels into forms that can be stored (glucose to glycogen, fat, a acids to proteins)
- promotes the storage of glycogen in the liver and muscle, and fat in the adipose tissue, and proteins in the muscle
what is the general role of insulin in the cephalic phase
lower levels of blood borne fuels (specifically glucose) in preparation for the impending influx
what is the general role of insulin in the absorptive phase
minimize the increasing levels of bloodborne fuels by utilizing and storing them
during which phase of enrg meta does the body secrete glucagon > insulin?
the fasting phase
`what do low levels of insulin cause?
what is the major secondary effect off this, and why?
glucose build up in blood, specifically because it has trouble entering most cells
saves glucose for the brain, bc neurons dont need it to intake glucose
what is a secondary effect of low insulin levels?
promote the conversion of glycogen and protein into glucose, called gluconeogenesis
what do high levels of glucagon promote?
what happens to brain cells if the second effect is maintained over time?
- release of free fatty acids from adipose tissue, along with their use as the bodies primary source of fuel
- conversion of these free fatty acids to ketones, used by muscles as a source of energy during the fasting phase
- if the body goes a long time without food, tho, the brain will also used ketones which further preserves the stores f glucose
define the set-point assumption
the belief that hunger (as motivation to eat) is always a response to an energy deficit (energy set point)
what occurs after a meal according to the set-point assumption?
what ends a meal?
energy resources are assumed to be near their set point, decline after
- eat until satiated (no longer hungry) which is believed to correspond to arriving at the set point
what are the three components of all set point systems
- set point mechanism
- detector mechanism
3, effector mechansim
what is the set point mechanism?
that by which the body defines a set point
what is the detector mechanism
that which detects deviations from the set point
what is the effector mechanism
that which acts to eliminate any deviations from the set point
what are all set point systems defined as? explain
negative feedback systems - feedback from changes in one direction elicit compensatory effects in the opposite direction
why are negative feedback systems common in mammals?
act to maintain homeostasis (stable internal environment) which is critical to survival
why were set point systems assumed to be necessary prior to the discover of adult brain plasticity?
what did this discovery do to the underlying logic of the set point system?
since the brain couldn’t change, energy resources had to be very regulated
made it seem less necessary
define the glucostatic theory
what is the primary piece of evidence
set-point offshoot that argued blood glucose is the set point measure,
- glucose is our brains primary fuel
define the lipostatic theory
what is the primary piece of evidence?
set-point offshoot that argued that each person has a set body fat percentage, deviations from which alter eating requirements so as to level out back to the set point
- adults weights stay fairly fixed
what is the relationship between the glucosattic and lipostatic theories?
complementary
- glucostatic accounted for meal initiation and termination
- lipostatic accounted for long term regulation
what are the three main problems with the set-point theory? evidence?
1 - (1)
2 - (3)
3 - (phenomenological 1)
- the evolutionary account - our ancestors main problem was inconsistency of food sources - doesn’t make sense that our hunger system is designed only to respond to immediate requirement, rather than future potential requirements (long term storage)
- major predictions just dont work - large reductions in glucose or body fat in lab animals that produce eating behaviours are never present to a similar magnitude in nature. lots of people have enough fat to survive for awhile, but eat anyways, and if we give ppl high calorie drinks before a meal they will still eat!
- fail to recognize the importance of influences such as taste, learning and social influences.
what is the positive-incentive theory of hunger and why did it arise/
bc of the failure to account for several hunger phenomena (the problems with set-point theories)
- postulates that hunger and eating are promoted by the positive-incentive value of eating, ie that we know it will make us feel good
is the positive-incentive theory of hunger one theory?
no, it is several that are considered the positive incentive perspective
according to the positive incentive theory of hunger, what is eating similar to?
sex - we engage in these behaviours because we crave them
what its he evolutionary explanation for the positive incentive theory of hunger?
unexpected food shortages have made us love to eat when there is good food around
what influences the degree of hunger at any given moment according to the positive incentive perspective?
what are some of these? (6)
the interaction of all the factors that influence the reward value of eating.
- flavour of food
- learned of effects of the food
- time since last feeding
- type and quantity of food in the gut
- whether or not there are other ppl around
- blood glucose levels
what is a major benefit of the positive incentive perspective?
doesn’t single out any one factor - there are lots
why are energy deficits not included among the list of factors that determine when/what/how much we eat?
because in our current situation (food-replete societies) we never encounter deficits of sufficient magnitude to actually stimulate hunger
why do humans prefer sweet, fatty and salty flavours?
sweet and fatty - typical of high energy foods rich in vitamins and minerals
salty - sodium rich
why do humans not like bitter tastes
denote foods rich in toxins
are human taste preferences universal?
no way jose
what are the two main ways humans and other animals learn what to enjoy
- prefer tastes that come with calorie influx, hate those hat make them sick
- conspecificis - species or culturally specific taste preferences that are learned socially
what are some examples of rats conspecific learning of food preferences
- like what is similar to tastes in mothers milk
2. like what they smell on the breath of other rats
what are the two ways animals learn to enjoy foods that contain necc. vitamins and minerals?
- sodium - deficiencies result in the craving of sodium rich food
- other - learn to like the effects of foods that contain the minerals, since they have no taste
Give an example of animals learning to enjoy foods rich in a mineral/ vitamin despite there not being any taste to it?
rats raised on a thiamine (B1) deficient diet will prefer a diet that has high B1 levels in it to one that is deficient bc of the positive health effects
what are the two main reasons that humans have so many vitamin and mineral deficiencies despite our ability to learn too prefer their health effects?
- lack of nutrients in market goods - companies produce tasty shit that isn’t any good bc it makes moe money
- variety of possible diets - if rats w B1 deficiency are offered 10 new dietary options, not a lot learn to prefer the thiamine one bc they cannot associate
what is a major difference between eating frequency in most mammals and humans
mammals prefer small snack sized meals throughout the day when there is ample resources, but humans (particularly those in large family groups) eat a few big meals
what is the association between typical meal time and hunger
we get hungry when we usually eat, and our negative symptoms of hunger are experienced when we miss such a meal
what is Wood’s position on premeal hunger
learning that a meal time approaches causes the body to enter is cephalic phase, releases insulin into the blood (decreases glucose)
thus, premeal hunger is the bodies preparation for the massive influx of nutrients prior to meal time, and the resulting homeostatic changes
describe the Weingarten study that supported Wood’s position on premeal hunger
pavlovian conditioning in rats - irregular feeding intervals began by a tone
when food is continuously present, the sheer presence of the tone caused them to eat, even if they had just finished
what is the motivational state that determines when we should stop eating
satiety
what induces satiety signals? what do their magnitudes depend on?
food in the gut, glucose entering the blood
- volume and nutritive density (calories per unit volume)
describe the findings on lab rats that demonstrate the importance and limitations of nutritive density
rats fed one baseline of consumption, then change nutritional density
- can adjust to preserve body weight until the density is reduced by more than 50% (lose weight) or major changes to palatability
what is the sham eating paradigm
artificially changing physiology to project food not into the stomach but just out of the body
what doe sham eating studies find?
what does this indicate about satiety?
contrary to the set point theory (meals should be huge if there is no change in energy), the first meal is the same as usually, but then they begin to increase slowly over time
- that it is a function of experience and learning
what is the appetizer theory, and what does it indicate about the set-point theory?
why does it work?
- small bites of food increase hunger, not the other way around
- buuulshit, this makes no sense under that view
- probs bc small amounts of food activate the cephalic phase response and prepare the body for calorie influx
how does serve size influence consumption
larger the serving, the more we eat
how do social factors influence consumption
we eat more in the presence of others, which is the same in rats
what is the effect of the cafeteria diet and what does this indicate? (2)
- cafeteria diets (lots of different tastes) increase caloric intake in rats by up to 84 percent, and body weight by up to 50 after 120 days
a) number of different tastes has a major effect on serving size
b) set pint theory is bs
what is the major conclusion fo the lab. results of the cafeteria diet?
satiety is very much sensory specific
- when we eat a lot of food a), our positive incentive for food a plummets, but for b and c it only goes down a bit, so if we can switch from a to b or c we are happy to. do so
describe the rolls study on sensory-specific satiety
- human volunteers asked to rate the palatability of 8 foods
- then ate a meal of one of them
- after the meal, asked to rerate the 8 foods
- rating of the meal they had eaten had declined way more than the other 7
- when offered a surprise second meal, ate most of it UNLESS it was the same type of food
explain the Booth study on sensory-specific satiety
- volunteers to rate the pleasure prod. by flavour, smell sight or thought of foods at times after consuming a large, high calorie high carb liquid meal
- immediate sen. specific decrease in the palatability of foods of similar flavour to the original meal right after consumption
- decrease in all palatability 30 minutes later
what is the general conclusion of the Booth study on sensory-specific satiety (2)
- signals from tase receptors produce an immediate decline in positive incentive value of similar tastes
- signals associated with the post ingestive consequences of eating produce a general decrease in palatability of all food
what did rolls suggest the two effects of sensory specific satiety are
- relatively brief effects that influence the selection of foods within a single meal
- relatively long term effects that influence of the selection of foods between meals
are the long term effects of sensory specific satiety universal among foods?
nope, rice, bread, potatoes, sweets, green salads can be mucked all the time with no palatability decline.
what are the two adaptive consequences of sensory specific satiety?
- encourages consuming a varied diet
2. encourages animals with access to a large variety of foods to eat a lot to preserve it in storage for less good times