Neural explanations for Anorexia Nervosa
People with higher levels of the neurotransmitter serotonin are known to experience more anxiety than those with more stable serotonin levels. One of the biological consequences of anxiety is the suppression of appetite. In fact, drugs which act on serotonin pathways in the brain are commonly used for the short-term management of obesity. AN has high comorbidity rates with OCD and depression, both of which are also associated with abnormal dopamine levels. Furthermore, dopamine is the neurotransmitter responsible for our interpretation of reward and pleasure from eating which explains their ability to maintain the disorder (never have cravings).
Neural explanations - Practical Applications
1) Firstly, it medicalises eating behaviour, which can help to reduce stigma for people who are obese or have eating disorders. By explaining their feelings of hunger (or lack of) as a biological process, it removes some of the personal responsibility. This may help people to feel better about themselves as their eating behaviour is seen as being beyond their conscious control.
2) Secondly, by understanding the neural mechanisms involved in eating behaviour, we could develop effective anti-obesity drug treatment. For example, learning how NPY interacts may help scientists to develop a drug to block NPY at receptor sites.
Neural explanations (AN) - Research (1)
BAILER ET AL:
Found high levels of serotonin in AN patients compared to healthy control groups. Furthermore, the highest amounts of serotonin were found in those patients who had the highest levels of anxiety, which supports the idea that unstable levels of serotonin increases anxiety.
KAYE ET AL (2001):
Found SSRI's, which reduce levels of serotonin, were effective in preventing relapse of recovering AN patients. This supports the view that stabilising serotonin levels is important in controlling anorexia levels.
Neural explanations (AN) - Research (2)
Found, using PET scans of 10 recovering AN patients, that they had increased levels of dopamine in the basal ganglia area of the brain, which is responsible for the way people interpret rewards. This supports the view that as you recover from anorexia your dopamine levels increase.
Neural explanations (AN) - Practical Applications
- If we accept the neural explamation of AN, then the implications for treatment are the use of drugs, in particular SSRIs. However, this approach to treatment is not always successful. It is most successful in reducing the risk of relapse in those patients that have stabilised their weight. However, SSRIs are least effective in patients who are most seriously underweight, suggesting that a more holistic approach to treatment is required.
- Neural explanations medicalise the disorder, which is less socially sensitive than other explanations, for example psychological explanations which can appear to blame family dynamics. This may help to reduce the stigma and encourage people to seek the help they need.
Sense of Smell research
- Found people who have a higher body mass index (BMI) have a greater sense of smell when it comes to food.
- Which would support the idea that there is a relationship between sense of smell and obesity.
ROLLS ET AL (2000):
Found that damage to the inferior frontal cortex limited, and even sometimes reversed, participants' ability to anticipate reward from pleasant odours. In other words, pleasant food odours were either not detected, or experienced as unpleasant.
Neural explanations - Sense of Smell
Feelings of hunger are not only triggered when our blood glucose levels are full. We can also experience a strong desire to eat when we smell food. The smell of food triggers an area of our brain called the inferior frontal cortex. This area of the brain receives messages via the olfactory bulb, which is responsible for our sense of smell. The inferior frontal cortex is responsible for our perception of how rewarding/enjoyable food is likely to be, and so the more active it is, the more likely we are to want to eat.
Evolution - Wider Issues (3)
The World Health Organisation (WHO) predicts that there will be 2.3 billion overweight people in the world by 2015, 700 million of whom will be clinically obese. You could argue that evolutionary explanations for food preference are unhelpfully deterministic, suggesting that people have little conscious control over their food choices. In fact, we know that there are many social, cultural and psychological factors which affect our food choice, including early learning experiences, mood and media, and these need to be taken into consideration to fully understand our complex relationship with food. We underestimate people's capacity to change.
Neural explanations - Homeostasis
The body needs to maintain an optimum equilibrium. The process of homeostasis should ensure that our blood glucose levels are sustained. This is achieved through a negative feedback loop. The brain sends signals that 'turn on' feelings of hunger when there is a drop in blood glucose levels, and are 'turned off' when the levels are restored, giving us feelings of satiety.
As part of this 'homeostatic explanation' for how we experience hunger and satiety, it is proposed that we quite literally have an 'on switch' that makes us experience hunger (the Lateral Hypothalamus) and an 'off switch' which makes us experience satiety (fullness), the Ventro Medial Hypothalamus. This idea is known as the dual centre theory (Hunger/Satiety feedback loop).
Homeostatis research (1)
TEITELBAUM & EPSTEIN:
- Found that damage to the LH caused aphagia (failure to eat) in rats, to the extent that they would starve themselves to death unless fed intravenously.
- Found that damage to the VMH caused hyperphagia (over-eating) in rats to the extent that they tripled their body weight in 3 months.
- This is support for the dual-centre theory.
- However, more recent research sugests that we need to understand the role of neurotransmitters, not just the physical areas of the brain, involved in controlling eating.
Homeostatis research (2)
- For example, the neurotransmitter Neuropeptide-Y (NPY), when injected into the hypothalamus of rats, causes them to begin feeding immediately even when they are full.
- This suggests that the neural mechanisms involved in controlling eating may be more complex than the dual centre theory suggests. We need to think about the neurotransmitters as well as the physical part of the brain.
Much of this research relies heavily on studies on rats and mice. This may mean that it lacks external validity because we cannot be certain about how accurate it is to generalise from animals to humans. Furthermore, it raises ethical issues, since there is widespread concern about the idea of replacing humans with other animals when it would be unethical to test on humans.
Neural explanations (AN) - Wider Issues
- Evidence from psychological approaches suggests that personality traits such as perfectionism may also trigger AN. It may be that being a perfectionist generates anxiety, and this, combined with abnormally high levels of serotonin and abnormal levels of dopamine may be the underlying cause of the disorder, suggesting it is an interaction of both nature and nurture.
- However a danger of biological reductionism is that we may overlook other factors that contribute to AN, in particular, the behavioural approach stresses the role of the media and our obsession with skinny role-models.
- It is also difficult to know whether neural abnormalities are the cause or the effect of the disorder.
Evolutionary Explanations for Anorexia Nervosa
1). ADAPTED TO FLEE HYPOTHESIS:
Some people were better at functioning when hungry than others, and during the EEA it would have been advantageous, as there was an unreliable food source, meaning humans would have to migrate to areas with more food, meaning that it is hard-wired and adaptive for some people to survive a long time without food.
2). THE REPRODUCTIVE SUPRESSION HYPOTHESIS:
Limits own chance of survival if there is another mouth to feed. By maintaining low body weight, anorexia can suppress their reproductive system, making them infertile.
For AN to have an evolutionary basis, then we would expect to find that:
- AN runs in families - the more genetically similar, the higher the risk
- Must be an evolutionary advantage to going without food
- Universal - across ALL class and culture
Cognitive - Research
FALLON & ROZIN:
Females had an 'ideal' much smaller than their 'current' and 'other attractive'. Males rated 'ideal' and 'current' most closer together and 'other attractive' smaller.
Those with an eating disorder tended to over-estimate their own body weight and had an 'ideal' lighter than the control groups. They judged that their body size had increased immediately after having a chocolate bar and soft drink compared to control groups.
Cognitive - PA & WI
Non-clinical groups have distorted body image but do not become anorexic.
The direction of causality is not clear because it is difficult to know whether distorted thinking is the cause of AN or the result of starvation. Starvation affects neural functioning that perception and vision becomes unclear.
P - However, there is a useful practical application for treatment. FAIRBURN has developed CBT which tackles AN by 'decentering' the client by encouraging them to stop seeing AN as their identity and to shrink the preoccupation with food and weight by encouraging them to value other areas of life that has been neglected.
Psychological explanations conclusion (AN)
AN is classified as a mental disorder in DSM, therefore understanding psychological factors that may trigger/maintain is important. However, not everyone is affected in the same way by environmental factors. Would suggest that some are more vulnerable than others - using diathesis-stress model. Some have an innate, genetic vulnerability. Avoiding reductionism, becoming more holistic.
Neural explanations - Wider Issue
However, this an example of biological determinism, and the problem with explaining eating behaviour purely as a response to neural mechanisms is that people may feel that there is nothing they can do to change their behaviour. This may be especially problematic for people whose eating behaviour presents a serious risk to their health or may even be life threatening. We know that there are many other social and cultural factors which affect our eating behaviour (including mood, early learning experiences and media), and so we should be careful about this level of biological reductionism.
Behavioural - PA and WI
Practical application - Educating vulnerable young girls about airbrushing (unrealistic media) and the effects it has on their behaviour.
Wider Issues - If recent 'natural beauty' campaigns take off then we should see a decline in the number of AN cases.
Probably not as simple as this because most people want to lose weight but do not become anorexic.
Wouldn't explain why you would continue to lose weight when the reinforcement has stopped and once thay have gone beyond the desired weight loss.
Behavioural - Research
BECKER ET AL:
A sample of adolescent Fijian girls stated a desire to lose weight following the introduction of TV in 1995.
YAMAMIYA ET AL:
Negative impact of media exposure can be prevented if teenage girls are educated about unrealistic body images in the media before being exposed to the media.
Evolution (AN) - Research
There is evidence that AN runs in families, which would support the view that it is at least partly inherited through genes:
HOLLAND ET AL:
Found that the more genetically similar you are to someone with AN, the higher your risk of developing the disorder, as shown by the concordance rates they found in their twin study - MZ= 9/16. DZ=1/14
However, the concordance rates were not 100% for the MZ twins, meaning that one has a vulnerability to the disorder, but the environment plays an important role - phenotypic plasticity.
Evolution (AN) - PA/WI (1)
P - These research findings can be applied to help us to reduce the amount of pressure within their environment. We can offer support and ways to manage the particular pressure that they may be experiencing and/or feeling.
W - If AN was genetic, a 'hangover' from the EEA, then in theory it should be universal (unaffected by class and culture). However, according to the Eating Disorders Association, AN is affected by class and culture, and is more common when adolescents are under pressure to achieve highly:
- One in 500 in state schools
- One in 100 in girls independent schools
- One in 55 in universities
- One in 10 in dance and drama schools
Evolution (AN) - PA/WI (2)
However, one of the biggest problems with evolutionary explanations for behaviour is that they are difficult to test using empirical methods. Evolutionary explanations are an abstract concept which means that they lack scientific status. We can hypothesise that those who inherited a genetic predisposition to being able to function whilst starving would have better survival chances than those who did not inherit this gene, however in order to test this hypothesis we would need to go back in time and conduct some controlled research, and clearly this is impossible.
Psychological explanations (AN)
- Principles of conditioning and social learning.
- Classical conditioning 'thin = desirable', 'eating = anxiety'
- Reinforcement for initial weight loss (operant conditioning)
- Vicarious reinforcement through media ideal
- 'Dieting gone wrong'
- Distorted thinking causes AN, for example:
- All or nothing
- Feelings of self-worth based on physical appearance/how well calories are controlled or limited
Evolution - Wider Issues (2)
Using evolutionary theory to explain food preferences is an example of genetic determinism which means that there is an assumption that we cannot over-ride innate drives with our own free-will. This is flawed as there are many individual differences in food preference, with some people choosing to be vegetarian or vegan, for example, for social, cultural or ethical reasons.
Evolution - Wider Issues (1)
1). Lack of scientific credibility:
However, the biggest problem with evolutionary theory as a scientific explanation for behaviour is that it is difficult to test. The opportunity to conduct controlled experiments is not there, as it is obviously impossible to go back in time! Much of the theory is based on assumptions and speculation about what is likely to have promoted survival and how. This speculation cannot be accepted as science due to a lack of emirical evidence.
Media - Practical Applications
- Educate young people about 'tricks' of the media.
- Encourage young people to avoid celeb culture.
- Expose young people to 'positive body image campaigns'.
3). These results indicate that, with as little as half an hour television viewing a day, the increase in snacking caused by food advertising would lead to weight gain of nearly 10 pounds a year. To encourage more healthy attitudes to snacking we should therefore avoid showing food adverts on TV if we accept that this is valid and want to consider reducing the risk of obesity.
Media - Wider Issues
Blaming the media for our unhealthy relationship with food is a point of view held by the behavioural approach. However, some would argue that this is unfair as we have free-will to make our own choices about how and what we eat and we are not passive digesters of media. However, the biological approach might argue that we are in fact hard-wired to seek out HFSS foods because from an evolutionary point of view, they would have helped in our struggle for survival. If this is true, we will seek out these foods regardless of what we see in the media.
Factors influencing attitudes - Mood
There are a number of possibilities to explain the effect of mood on eating behaviour:
- Some foods (eg. chocolate) stimulate dopamine and other 'pleasure chemicals' giving us an immediate high.
- Foods that are high in sugar and salt taste better (to most of us) giving us instant pleasure, lifting us out of the dumps.
- We have been classically conditioned through advertising or by our parents that certain foods are 'comfort foods' (a form of affective conditioning).
Mood - Research and Wider Issues
R - GARG ET AL:
Found that when people watched a sad film, they consumed 36% more buttered popcorn, whereas those watching the happy film consumed significantly more grapes. They concluded that sad people need an 'instant kick', whereas happy people want to maintain their good mood for longer so make 'better' food choices.
W - Research into the factors that influence our attitudes to food and eating is problematic and can lack scientific credibility. In order to attain scientific status, it is often conducted in highly controlled conditions in a lab study, in which case it may lack ecological validity as it may not reflect the choices that people would make in real life. However, simply asking people about their attitude to food is unsatisfactory since there is a lack of empirical evidence to back up what they say. It is also likely that self-report techniques will result in socially-desirable responses. None the less, this field of research teaches us that our relationship with food is complex and trying to understand it is likely to be important to our long-term health and well-being.
Media - Research
1). FIELD ET AL:
Found that constantly looking at fashion and beauty magazines can lead to becoming constant dieters.
3). YALE UNIVERSITY:
Found children aged 7-11 who watched a cartoon including food commercials ate 45% more snack food while watching the show than children who watched the same cartoon with non-food commercials.
Factors influencing attitudes - Media (2)
So powerful is the media in influencing food preferences and eating behaviour, in 2006 Ofcom found it appropriate and necessary to adopt restrictions intended to reduce the exposure of children under 16 to advertising of HFSS foods in the UK. In America, Disney have recently announced that they will phase out all marketing of HFSS foods on their channels over the next few years.
3). Encourages 'mindless eating' - whether we are hungry or not:
Children and adults who watch TV ads, especially those for unhealthy products, are more likely to snack on foods at hand, and are potentially at higher risk of becoming obese, according to Yale University.
Factors influencing attitudes - Early Learning Exp
- Conditioning: If a food is present as the same time as a reward the child will associate the food with the reward and become more likely to enjoy.
- Exposure to food: Children initially show neophobia when encountering new foods, but the more they are given them, the more familiar they become and the more likely they are to like them.
Early experiences - Research (2)
Looked at 400 low-income women with children aged 1-3 enrolled in Early Head Start programmes in the US. Results showed toddlers were less likely to consume fruits and vegetables four or more times a week if their mothers did not consume that amount. She concluded that what and how mothers eat is the most direct influence on what toddlers.
This supports the idea that parents are role models for their children (SLT).
P - On the basis of this research, we could encourage parents to sit at the table with the children, eat what they are eating and not resort to bribery.
Factors influencing attitudes - Media (1)
1). Makes people feel dissatisfied with their body image:
- Unrealistic body images are seen as the 'norm'.
- This can trigger an idea to diet and have an unhealthy attitude towards food.
2). Conditions us into associating certain foods with a lifestyle/mood:
It is a term known as affective conditioning in which we are distracted away from the actual product by being encouraged to associate it with a particular life style/humour/character. This tactic is usually used when the reality of the actual product is difficult to sell. HFSS (High Fat Salt Sugar) foods are a good example of this.
Successes and failures of dieting (1)
Theory 1: Restraint Theory (HERMAN & MACK)
- 'Restrained eaters' use a 'self imposed cognitive boundary' to make decisions about what, when and how much to eat. this means that they make a decision (often with the help of a commercially available diet such as Weight Watchers) to 'allow' themselves a certain amount of food each day.
- The 'restrained eater' uses the self imposed cognitive boundary to over-ride natural, physiological boundaries that are set by the body. In other words, they ignore genuine feelings of hunger and fullness. This means that they may not eat when they are hungry, because they are 'not allowed' any more calories or they are 'saving up' their allowance for later. If you do not eat when you are hungry, there are two potential problems...
Successes and failures of dieting (2)
1. When you are hungry, you crave HFSS foods as your body needs the calories.
2. Over-eating. You eat more quickly and it takes you longer to feel full.
These, according to restraint theory, are the two main reasons why dieting often doesn't work. Furthermore, if the 'restrained eater' does 'give in' and eat even though they feel that they are 'not allowed', they are likely to experience the 'What the hell effect'
What the Hell effect: When someone is so hungry that they give in and eat HFSS foods. Because they feel guilty, they give in completely and start again the next day. Can trigger a binge eating.
Evolutionary Explanations for food preferences (1)
- During the Environment of Evolutionary Adaptation (EEA) period, humans have adapted to favour certain food preferences for our survival.
- Firstly, humans are more likely to favour high calorie and high fat foods. This was because the food source was unreliable and we were much more active as we had to hunt for food. The high fat and calories provided us with enough energy to last until the next meal.
- Secondly, sweet tastes are naturally favoured as they reduce the risk of being poisoned, which happens in some bitter foods.
- Thirdly, meat was favoured during the EEA as the amino acids found within the meat helped our brains to develop, causing us to evolve into the intelligent species that we are today.
Evolutionary Explanations for food preferences (2)
- The fourth food preference we have adapted to prefer is a savoury flavouring called umami, which contains protein, which was neccessary for our survival. This can be artificially manufactured today in the flavouring MSG.
- Finally, a mechanism that we have adapted, known as taste aversion, helps us to avoid any foods that have made us ill in the past.
Evolution - Research (1)
- If it is true that there is an evolutionary basis for our food preferences, then we would expect it to run in families.
KESKITALO ET AL:
- Found that a 'sweet tooth' runs in families
- Although you could use this to support the biological basis, it could be behavioural. Its difficult to know if you can use this to support the theory. Cannot rely on this research to support the evolutionary argument.
DESOR ET AL:
- Even 3 day old infants demonstrate this preference - innate
Evolution - Research (2)
BELL ET AL:
- Gave sweet sugary foods to Eskimos in Northern Alaska who had previously lacked sweet food and drink in their diets.
- They found that, in all cases, cultures previously without sugar did not reject the sugar containing food and drinks of the culture, suggesting that a preference for sweet tastes is not culturally learned.
This research can be used to support the idea that food preferences are largely innate (not determined by culture and experience) and inherited (a genetic predisposition), all of which supports evolutionary exlanations for food preferences.
Practical Application/Wider Issues (2)
- However, not all diets fail, and these cognitive theories are limited in their ability to explain why some people (eg. those with Anorexia Nervosa) are able to quite literally starve themselves. This may require a more biological explanation, whereas the explanations offered by restraint theory and denial theory rely heavily on the cognitive approach. This is an example of cognitive (sometimes called machine) reductionism.
- Finally, there is a strong gender bias in this research, with much of the research relying on female participants. It may therefore lack population validity because we cannot be certain that men experience the same cognitive process in their experiences of dieting.
Practical Application/Wider Issues (1)
- 'Anti-dieting programmes' - encourage mindful eating, learning to natural physiological boundaries, eating a balanced healthy diet (rather than a calorie restricted diet) and exercise.
- The research in this field may lack validity because it is difficult to test people's genuine eating behaviour: If you use experimental methods (as in the preload/taste test) the problem is it lacks ecological validity - very false environment. People's food choices in an experimented situation may not reflect real life food choices
- However, if you rely on self-report techniques (such as interview, question, food diaries etc), the problem is... that the more aspect of having to keep a food diary affects their eating behaviour (Hawthorn effect) - not lying but not maintaining diet. Socially-desirable responses - appear more healthy than you are.
Successes and failures of dieting (3)
Theory 2: Denial
Denying yourself a particular food group can lead to you obsessing about that particular food, making cravings strong and making it difficult to resist.
The destructive process of denial (often called the 'ironic process of mental control'), can then be combined with restraint theory to offer a comprehensive explanation for why dieters are prone to binge eating.
Restraint Theory - Research (1)
HERMAN & MACK:
- Used the 'preload/taste test' to demonstrate the 'What the Hell'. In experimental conditions, they gave restrained eaters (dieters) a 'preload' of high calorie food (milkshake), and then gave them the oppurtunity to eat as much ice cream as they wanted whilst secretly observing how much they ate.
- They found that dieters ate significantly more ice cream than the non-dieters because they experienced the what the hell effect and are more likely to over-eat.
Restraint Theory - Research (2)
- Found further evidence for the 'what the Hell effect' by manipulating the size of a pizza slice using the same 'preload/taste test' method outlined above. During the pre-load, dieters given a pizza slice smaller than other people's then ate less cookies in the taste test. This is because if they thought they had eaten a bigger slice, they felt bad, so the what the Hell effect triggered a binge. If the slice was smaller, they felt more control and felt positive and motivated.
Denial - Research (1)
WEGNER ET AL:
- Asked half of his participants not to think about a white bear, and the other half to think about a white bear. He told all of them to ring a bell every time they thought about the white bear whilst they were doing some other distraction task.
- Those told not to think about a white bear rang the bell significantly more often than those told to think about the bear.
- This supports the theory that if you try to deny yourself something, you are more likely to do it.
Factors influencing attitudes - Early Learning Exp
- Infants like sweet tastes and are born with taste receptors for sweet, sour, salt, bitter and umami (savouriness), meaning they can tell what is sweet and what isn't.
- As children are weaned off breast milk, and once they are old enough to express a preference for certain foods, it can be difficult for parents to encourage children to eat a diverse range of foods, particularly as they naturally have a sweet tooth.
- The behavioural approach states that how parents manage the challenge of getting their children to eat a balanced, healthy diet, can have a long term effect on their attitudes to eating and their relationship to food.
- In addition, SLT sees parents as important role models, and research suggests that how well our parents model positive attitudes towards food will have a positive effect on our own attitudes as we grow up.
Early experiences - Research (1)
Found that eating dinner together at a table with their parents made children feel more secure about themselves, encouraged good nutrition, and lowered the risk of eating disorders and obesity.
This supports the view that parents can be positive role models for infants.