Diet - Mood
WANSINK- Offered 38 pps the choice of hot buttered popcorn or grapes. They were split into two groups, one watched a happy, upbeat film, the other, a sad film. Those watching the cheerful movie ate more grapes and those in the sad movie ate more popcorn. They thought this was because those in a bad mood seek to quickly ellivate this with the use of fatty, sugary food and those already in a good mood, seek to prolong this long term so eat healthy food.
+ High control
+No order effects/ demand characteristics
+Pps asked to record their mood afterwards (increases reliability)
- Independent differences (taste, how the movie affects them)
- Social desirability bias
- Small sample.
- Low EV
Diet - Mood (Continued)
WANSINK - wanted to see if nutrional information made a difference to food consumption.
Info No Info
Happy normal 2x as much
Sad ate less than above. 2x as much as above.
When given nurtional information, pps ate less and those in the sad film ate even less than those in the happy one. Without the info, they ate twice as much, pps watching the sad film ate twice as much as those watching the happy film.
Diet - Health Concerns
- Many people are keen to eat foods considered healthy and to reject food considered unhealthy.
MONNEUSE - Demonstrated the importance of health concerns by giving pps a taste test. He found those who preffered the dairy products with medium/high sugar content actually chose lower sugar options due to health concerns.
TUORILA and PANGBORN - Used questionnaire data on womens intended and actual consumption of milk, chese and ice cream. They found the actual consumption was based more on liking than health concerns.
STEPTOE - Put into rank order the factors that pps say they take into account when choosing what to eat.
- Seonsory appeal
Diet - Cultural factors
Our cultures and subcultures to which we belong can be highly influential on our choice of food. However many cultures have little food choice and people eat what is available to aid survival e.g inuits eat seal, polar bear and fish which are high in protien and fat and low in carbs.
WARDLE - Surveyed the diets of 16,000 YA across 21 european countries. He found Scandinavians eat more fibre than southern meditteranean countries which eat the most fruit. England and Scotland eat the least, Poland and Portugal eat a higher salt intake than Sweden and Finland.
The mediterranean has lower levels of obesity and heart disease due to their diet which consists of lots of fruit and veg, olive oil instead of fat, lower levels of cheese, dairy, fish and chicken and low levels of red meat and wine.
However, this was found out using questionnaires so may be suseptable to social desireability bias, perception and reality and appetite varies.
Diet - Cultural factors (Continued)
PIMA INDIANS- Those who stayed in their community had lower levels of obesity compared to those who moved to areas influenced by american culture.
BEDOUIN WOMEN - Have higher levels of carbs, protien and salt. Those who stayed in the desert of Arabia and those who moved away to a more urban setting varied very little.
Diet - Success and Failure of Dieting
25 - 30 is an overweight BMI. >30 is obese.
BARTLETT- Reported that 65% of americans can be classed as overweight or obese.
World Health Organisation - Found that 61.5% of UK are overweight and 24% obese.
Weight related conditions are second only to smoking as a preventable cause of death.
PERRI and FULLER- Did a meta-analysis of diet studies from 1970-1990 and found they resulted in pps losing 5-10% of their body weight.
LOUIS-SYLVESTRE- Reported that dieting can work better when we eat more smaller meals so that same amount of calories is consumed over a day. In France, a fourth meal is eaten by children and some adults at tea time. Missing the meal seems to lead to a higher BMI. People who eat the 4th meal have a higer carbohydrate intake and a higher metabolism.
Diet - Success and Failure - Success
- Change to moderate rather than low fat as its not as big a change, still tatses nice and you wont feel punished.
- Goal setting - not too ambitious, attainable short and long term goals.
- New eating and lifestyle habits so it lasts.
- Social support.
BARTLETT - When pps are motivated and recieve postitive feedback, they are more likely to achieve target weight which acts as a reward itself.
MILLER-KOVACK - Social support methods offered by weight watchers are superior to individual dieting regimes.
Diets might work short term but over a period of time, a restricted calorie diet begins to draw on reserves from muscels. If you lose muscel mass, your metabolic rate slows and you burn fewer calories and weight loss slows.
MANN - Carried out a meta-analyisis of 14 studies that followed pps for at least 4 years after a diet. Average weight loss was 14kg and by the long term follow up, pps had gained back all but 3kg.
Diet - Success and Failure - Failure
WILLIAMS - People who have problems maintaining concentration are less succcessful with their diets, presumably as they lose focus on the target and behavioural strategies they should be undertaking.
Genetic Predisposition - People find it harder to burn calories and lose weight although they excersice regularly. Other genes can stop people realising theyre full and so they keep eating.
Set Point Theory- Suggests our body has a particular range of weight that it is comfortable in, usually about 10% of a persons body weight range in which your weight can fluctuate. When we try to lose weight, the body will let it happen for a time, but then it starts fighting back
- Studied in western cultures. (EUROCENTRIC bias).
- Esocentric, mainly women who worry about weight and go on diets.
Diet - Biological Explanations
Neural Mechanisms- A biological function in the brain that tells you if youre hungry/full.
Hypothalamus - A part of the brain that functions to retain homeostasis (body temp, metabolic rate, pressure etc.)
Ventromedial Hypothalamus- Part of the hypothalamus. Stimulation is thought to lead to the termination of eating behaviour. Damage = excessive food intake.
Leptin - A hormone produced by fat cells and is involved in regulation of appetite. Tells us were full.
Lateral Hypothalamus - Part of hypothalamus, stimulation thought to lead to the onset of eating behaviour. Damage= reduced food intake.
Ghrelin- Hormone located in the stomach and makes you fel hungry.
Satiety - When you are no longer hungry.
Lesion- Damage to the brain.
Diet - Biological Explanations (Continued)
FRIEDMAN - Isolated the satiety molecule leptin in 1994.
COLEMAN- Research suggested a defincency in the "ob" gene (dont produce leptin) lead to some mice being obese. Coleman confirmed this when he discovered a mouse, named "db", with a genetic mutation of the ob mouse. He used parabiosis to try and decipher what it was causing the abnormal weight.
Ob + Normal = Ob lost weight.
Normal + Db = Normal starved.
Ob + Db = Ob lost weight.
Ob mouse = Functioning satiety center but no leptin signals.
Db mouse= Working leptin signals but abnormal VMH.
Diet - Biological Explanations (Continued)
LONDON - Gave leptin replacement to 3 adults with the ob gene mutation and found that it normalised weight and feeding behaviour. Using MRI scans, leptin replacement was paired with food cues and it appeared to lower brain activity in the parts involved in appetite and heighten activity in areas accosciated with satiety.
Diet - Biological Explanations (The Hypothalamus)
Located above the pituitary gland mid-brain.
HETHERINGTON and RANSON- Published a famous study on the control of eating behaviour. Demonstrated that a lesion on a rats hypothalamus caused it to overeat and become dramatically obese. This involved the VMH and the assumption was this was the satiety centre.
ANAND and BROBECK- Found that a lesion on the lateral hypothalamus led to a loss of feeding behaviour. Suggests this is necessary for signalling hunger.
These results led to the dual centre model. Suggets we have a homeostatic perception of hunger and satiety.
Diet - Biological Explanations (The Hypothalamus C
TEITALBAUM- Rats had to push a bar an increasing number of times (up to 256x) in order to recieve a food pellet. When they lesioned the VMH and compared bar pressing to control group, they found the VMH rats wouldnt feel full and kept pushing. However though initally wokring harder, the became lazy and choosy, they ate less pellets when they tasted stale and bitter.
Your cultural schedule and environment alert you to when to eat. For those on a restricted schedule due to work/school, your body becomes accustomed to eating at a certain time and you may salivate. When off this schedule, the taste and smell of food act as signals.
CUMMINGS- Assesed ghrelin levels every 5 minutes and pps assesed hunger levels every half hour. 5/6 showed a relationship between ghrelin and hunger levels.
Diet - Biological Explanations (Satiety Signals)
Meal size- Prescence of food in the stomach signals fullness. As food leaves, a hormone called CCK is realsed and acts as a hunger suppresant.
Injections of CCK in animals and humans reduce meal size however research has shown that rats and humans eat more tastier food than non tasty and they eat more in comapny suggesting not just biological factors play a part.
Body weight- As more fat is produced, so is more leptin and the hypothalamus is stimulated to reduce food intake.
Diet - Evolutionary Explanation
We can identify food that we need and reject those that may be dangerous.
Taste and Smell.
Olfaction = Smell Gustation = Taste
Salty- Helps cells function
Sour- Identify harmful food
Bitter- Detect poison
We are omnivores as we were orignally hunters and both meat and veg are vital for us to stay healthy. Meat is a good source of protien, large kills would mean less time spent foraging and was readily available.
Diet - Evolutionary Explanation (Continued)
As hunting was vital to our survival, good hunting skills became desirable in a mate and so the hunters were more likely to be higher in status and have more children.
We learnt through CULTURAL TRANSMISSION that spices and cooking made meat safer and that bad meat tasted different. This helped us stay healthy.
Neophobia- Fear of new.
FROST- Offered pps. a choice of 5 mixed smarties or 5 of the same colour. The majority chose the mixed.
GARCIA- Used wolves to test TASTE AVERSION LEARNING. Gave them lamb which was mixed with a mild posion and covered in sheeps skin. Sick. When allowed to approach sheep, they avoided them.
Rats were posioned at the same time as they ate foods both familiar and unfamilair. They later avoided the unfamiliar food.
Diet - Evolutionary Explanation (Morning Sickness)
Occurs in the early weeks when the baby`s organs are developing. Foods such as eggs, caffiene, alcohol, sushi, shellfish and some veg are avoided.
PROFECT- Believed this was caused to prevent toxins harming the baby.
-Hard to compare.
-Information based on fossils- Missing link.
-Ignores cultural transmission.