Hunger and eating Flashcards
Human digestive system
Mouth and salivary glands
- Mastication (chewing) and saliva (alkaline)
Oesophagus
- Transporting food to stomach
- Set up for alkaline conditions, so acid from the stomach can damage it
Stomach
- Churning food and breaking it down
- Acid digestive enzymes
Liver/gall bladder
- Additional digestive enzymes added into the small intestine
Pancreas
- Produces insulin and glucagon to store and release energy
Small intestine
- Absorbs most nutrients from the food that we eat
Large intestine
- Removes water and packs waste
Liver and kidneys
- Filter out toxins for excretion
Takes 12-14 hours
Key pancreatic hormones
Insulin
- shifts carbohydrates from the blood to storage- releases energy
Glucagon
- Shifts fuel from storage to where it is needed to fuel body
- Converts glycogen and proteins to carbohydrates
- Frees fat stores to use as fuel when the glucose stores are low
Outcome of digestion
Lipids/fats- stored at fats
Amino acids- Stored as proteins (mostly in the form of muscle tissue)
Glucose- stored as glycogen in the muscles and liver
Homeostasis
Detectors in our body tell us when we are running low on nutrients/fuel, and trigger our biology and behaviour
Brain is sensitive to shortage of glucose (hypothalamic regulatory nuclei)
Liver is sensitive to shortages of glucose and lipids
Stomach sends signals to the brain (release of ghrelin). Need for food if it is unstimulated
Part 2
When we are running low on fuel, we experience
Hunger (a motivational state)
Craving
The body corrects by
Releasing glucose
Taking in more food
Satiety
The body generates a range of short-term satiety signals
- Adequate glucose and lipid acid levels- detected in the brain and liver
- Stomach distension- stretched stomach
Buccal activity - Lots of chewing
-High levels of sensory stimulation- Big on taste and smell
Appetite suppressant chemicals - Caffeine
Diet products try to offset the first one with the others
Long term satiety signals
Fat tissues secret a hormone- leptin
- Increases body metabolic rate
Decreases food intake by:
- Desensitising the brain to hunger signals
- Inhibits the effect of other hormones that drive eating- particularily Neuropeptide Y
Satiety cascade
Sensory- chewing/spicy food
Cognitive- e.g. you’ve had a full plate of food you shouldn’t go back for more
Post-ingestive- your stomach feels full
Post-absorptive- can only occur when you’ve had enough food
Minnesota starvation experiment
Men either joined the army or took place in a starvation experiment
Nutritional deficits
- Scurvy, rickets
Concentration/cognitive
Social effects
Physical and mental development
Emotional instability (mood swings)
All physical systems e.g. reproductive system
Developed binge eating- satiety and hunger was messed up
If a baby is breastfed by someone that was starved, this can predict obesity in the baby The breastmilk doesn’t have many nutrients so the baby has to suck harder- the early environment is priming the child to get as many nutrients as they can
Genetics
Makes us more likely to eat specific foods
We can learn to like other tastes but it takes longer
Predisposed to high-energy, high taste foods as they are more likely to contain nutrients
Less likely to enjoy bitter foods as they are more likely to be toxic
Learned taste preference and aversions
Culture- foods can be common in one culture but rare in another
Upbringing- foods experienced early tend to be more readily approached
Satiety to specific foods- I had pizza yesterday I don’t want it today- keeps our diet varied
Social learning
Imitation of what and how others eat:
Types of food
Specific foods
Speed of eating
Amount eaten
Environmental factors
Lighting- we eat more in dim lighting
Temp- we eat more when cold, less when hot
Portion sizes
Smells of the food and the environment- makes you hungry
Location/proximity of food
Agriculture and food industry
Ensuring that we are not starved due to the increasing population- The malthusian hypothesis
Food industry is a toxic place
Selling processes food that is relatively cheap in large quantities to ensure profit margins- often fatty and sugary foods
Premium prices on more healthy foods- often out of season which is not good for marketing
Farmers were subsidised to grow corn, bit the government needed to do something with all the corn- created a market for high fructose corn syrup- supplied for cheap use in products- related to obesity levels
Morgan Spurlock- Ate 3 meals a day at mcdonalds- had to have the supersize option if they offered it- he gained 11kg in 30 days- had high cholesterol, food swings, developed a fatty liver
