hunger eating and health Flashcards
evolution and digestive system
evolutionary to make the most from the food that we eat → extraction of nutrients effectively
digestive system
* mouth and salivary glands
* oesophagus
* stomach
mouth and salivary glands
* mastication and saliva (alkaline)
* break down food
oesophagus
* transport to stomach
* alkaline conditions - acid from stomach can damage this
stomach
* churning and break down of food
* acid digestive enzymes
digestive system -
* liver / gall bladder
* pancreas
* small intestine
* large intestine
liver / gall bladder
* digestive enzymes added into small intestine
pancreas
* produces insulin and glucagon to store and release energy
small intestine
* absorbs nutrients from food (majority)
large intestine
* removes water and packs waste
digestive system
* liver and kidneys
* rectum/anus and bladder
liver and kidneys
* filter out toxins for excretion
rectum/anus and bladder
* store and expel waste
pancreatic hormones (2)
insulin
* carbs from blood into storage - fast release energy
* carbs (glucose) → glycogen, proteins
glucagon
* fuel from storage to blood
* glycogen and proteins → carbs (glucose)
* frees fat stores (fatty acids) - use as fuel when glucose stores are low
* carb → fat → protein = order of fuel release
diabetes have issues with either of these hormones - with store or release
human complex food intake - macros
omnivorous - so need the range of foods
macro nutrients:
fruit and veg
carbs
dairy
protein
fats
eating macros will mean we get all necessary micros
variation between (number of stomachs) and within species (dairy tolerance)
product and storage mechanisms: lipids and fats
stored as fats
largest and most efficient energy store
not quick release energy like carbs
product and storage mechanisms: amino acids
stored as protein
mostly in form of muscle tissue
product and storage mechanisms: glucose
stored as glycogen
in muscles and liver
fast release energy
product and storage mechanisms: micros (vits and mins)
body structure
bones, cell structure etc.
get these from eating a balanced diet
mechanisms to ensure needs are met
evolutionary → developed to balance intake and output
hunger and craving to make you eat specifically
homeostasis → when set point is violated
fat metabolism will change to push up or down to the set point
signalling:
* brain → sensitive to glucose shortages, hypothalamic regulatory nuclei
* liver → sensitive to shortage of glucose and lipids
* stomach → signals to brain (grehlin release) to communicate need for food if it is unstimulated
example = running low:
* hunger (motivational state) - from low fatty acid and glucose levels
* cravings (automatic behavioural state)
body correction for this:
* release of glucose
* take in more food
where eating optimum goes wrong
internal factors - learning, emotions
environmental - toxic environment
satiety - short term signals from body (5)
adequate glucose and lipid acid levels
detected in the brain and liver - therefore stop eating
stomach distension
can also feel from anxiety
buccal activity
lots of chewing
high levels of sensory stimulation
big on taste and smell
appetite suppressant chemicals
e.g., caffeine, amphetamines
satiety - use in diet medications
try to offset adequate glucose and lipid intake by stimulating the other signals (don’t work long term) - limited temporary success
is there a satiety brain centre
previously thought in the hypothalamus (or other areas depending on different studies
recent evidence = no centre
more hormonally controlled
- ghrelin, neuropeptide Y, serotonin
long-term feedback mechanism of fullness
fat releases leptin
increases metabolic rate
decreases food intake
desensitises brain to hunger signals
inhibits effect of other hormones that drives eating (particularly neuropeptide Y)
satiety cascade
sensory
→ early signals saying you have had enough food, sensation of fullness, chewing food
cognitive
→ know you’ve already eaten a lot
post-ingestive
→ food hasn’t been absorbed but you know to not eat more
post-absorptive
→ signals from absorption of food to stop eating
this is why gum doesn’t work long term as you don’t feel full after chewing
ghrelin vs leptin
leptin = from fat
stops intake of food - satiety
ghrelin = released by stomach
from hunger - stimulates eating
health implications of normative poor eating - Dutch hunger winter (1940)
study of victims of hunger winter where there were no supplies
health implications of normative poor eating - minnesota starvation experiment
people either had to join the army or take part in starvation experiment (coercion…)
studied effects of starvation on 35 men:
* cognitive, social, emotional effects of starvation and weight gain
* gaunt, extremities filled with fluid, dizziness, depression, lack of energy, became food obsessed, more irritable
* rehab after experiment was difficult → weight continued to drop even with more food - kept feeling hungry
* some took 2 years to recover physically and mentally after the 6 months of eating 1800 kcal a day
base understanding of anorexia on these studies - the lack of food fuels the obsession as well as the mental disorder itself
starvation effects
nutritional deficits - scurvy, rickets etc.
starvation effects can be immediate, long-term or both:
concentration/cognitive
social
physical and mental development
emotional instability (tryptophan cycle)
all physical systems
starvation effects can cross generations
* obesity in children of starved mothers - limited availability of nutrients in early environment from breast milk
effects of obesity
affects social functioning
strong link with premature mortality
related to specific problems in children:
bullying, school absence, shame, stigma, self-esteem
factors that take body away from homeostasis (6)
genetics
learning
social learning
environmental factors
social pressures
food industry
toxic environment
factors that take body away from homeostasis - genetics
more likely to eat particular foods
learn other tastes but they take longer - grown-up tastes e.g. olives, acid foods, broccoli
predisposed to like high-energy, high-tase foods - sweet, fatty, and salty - more likely to contain nutrients
less likely to enjoy bitter foods - association with toxicity
factors that take body away from homeostasis - learning
culture → common foods in some are not in others
upbringing → food experienced early tend to be more readily approached
satiety to specific foods → don’t want to eat same foods multiple times in a row, keeps diet varied
factors that take body away from homeostasis - social learning
influenced by what is going on around you
imitation of what and how others eat
types of food, speed and amount of eating
powerful cultural influence - eat what you perceive as normal/local/customary
factors that take body away from homeostasis - environmental factors
lighting - eat more in dim light
temperature - eat more when cold than hot
portion sizes - what is portrayed as normal
smells - of food and environment
location and proximity of food
factors that take body away from homeostasis - agriculture and food industry
food industry goes through stages in level of positive/toxic influence
purpose = ensure we aren’t starved due to increasing population → Malthusian hypothesis (predicts human race would starve as we cannot produce enough food to fuel population - disproven in most countries)
currently toxic:
* selling ultra-processed foods for cheap
* large quantities, ensures profit margins, fatty and sugary foods
* puts premium prices on more healthy foods - fruit and veg often out of season and so costs them more
factors that take body away from homeostasis - agriculture and food industry as toxic example
Nixon in 1970s subsidised growth of corn
high fructose corn syrup became huge product in US due to high levels of corn
sold cheaply and used in everything instead of sugar
increases risk of fatty liver disease, decreased insulin sensitivity, precursor for gout, obesity levels
HFCS doesn’t give you same energy as sugar does - leads to overconsumption
factors that take body away from homeostasis - toxic environment example - supersize me
man ate three meals per day at McDonalds - supersized if it was offered to him
in 30 days gained 11kg, high cholesterol, mood swings, fatty liver
factors that take body away from homeostasis - toxic environment
describes how human evolution and environment we are in now are at odds
* food scarce cultures - obesity is a status symbol
* food plentiful cultures - obesity is stigmatised as sign of weakness
evolved to get food where you can - high-energy food only seasonally available so eat high-fat/salt/sugar foods where you can - to build up fat stores
past 50-60 years - environment change pushed us to obesity risk, easy to access food, food industry puts lots of sugar/fat/salt into food → cheaper and more palatable
* liquid calories too
lack of exercise - screen time - advertising for food and drink → dissociative effects, reduces self-control
intergenerational effects of this seen
