Biological Explanations into eating behaviour PSYA3

Homeostasis.

• Homeostasis is when the body detects the internal enviroment in the body and corrects it.
• The body includes a turn on and turn off mechanism in eating. (See mind map on neural mechanisms)
• The Lateral Hypothalamus control the hunger side of eating. Damage to the hypothalamus in rats showed aphagia which meant that they wouldnt eat.
• The neurotransmitter neutopeptide Y is important for turning on eating and can be found in the hypothalamus.
• The Ventromedial Hypothalamus control the satisfaction side of eating. Damage to the hypothalamus created hyperphagia which meant they overate.
• However damage to the nerve fibres passing through the VH can damage the Paraventricular Nucleus which can cause hyperphagia.

Homeostasis.

• Neural Control of Cognitive factors.
• The amygdala is the part of the brain recognises previously eating food.
• When the amygdala is removed in rats they eat all food whether they had eaten it before or not. But when in tact they dont eat unfamiliar food.  (Rolls and Rolls)
• The inferior frontal cortex receives messages from the olfactory bulb which is responsible for smell, because odours influence taste.
• Damage to the IFC is thought to decrease eating because it diminishes sense to food odour and therefore taste too.

Homeostasis.

• Research conradiction.
• For this theory to be applicable to the real world it needs to both anticipate and prevent energy deficits not just react to them. It must promote levels of consumption that maintain bodily resources over a certain level and to prevent it going below the food availability line.
• Damage to the LH caused deficits in other areas such as thirst and sex not just hunger.
• Genetically manipulated mice did not produce NPY and results showed there was no significant drop in eating behaviour. (Marie)
• Research Support.
• Damage to the VMH caused hyperphagia in other species not just humans.
• Kluver-Bucy syndrome have damage to amygdala and inferior prefrontal cortex.

• An Evolutionary Approach- Its suggested that the primary stimulus for hunger and eating is goods positive incentive value, i.e we develop tastes that in nature will aid out survival.
• Real World Application- One of the main reasons why people overweight continue to eat is because the brain produces NPY in excessive amounts this tells us that individuals are constantly hungry. Also other researchers have found that NPY is also produced by fat cells in the abdominum causing a viscous circle of over eating.
• Stress and hunger- Research shows that the body produces extra Gherlin in response to stress. However while Gherlin acts to reduce stress it also increases appetite which can lead to comfort eating. Reducting Gherlin could reduce eating but increase problems with stress.

The Evolution of food preferences.

• The Enviroment of Evolutionary adaptation (EEA) 2 million years ago.
• The early diets consisted of animals and plants. Fatty foods would have been used to keep alive. This explains why we have evolved a preference for food high in calories.
• Meat was introduced to diets to replace the lack of plants. Its thought that without the introduction of meats, humans wouldnt have evolved into the active and intelligent species they are today. (Milton)
• Bait shyness was discovered by farmers who were trying to get rid of rats by putting down poison to stop them eating the food. Once the rats got ill off the food they didnt try it again.
• The medicine effect was the opposite of bait shyness where a food they ate while recovering from an illness 'helped' them get better, they prefered it in the future.

The Evolution of food preferences.

• Research Support.
• Fruit and Veg was chosen by the EEA not because of how sweet it was or the protein but because of the high calorie content. (Gibson)
• Taste aversion can be linked to other species not just humans. This is called biological preparedness and meant that species had the ability to learn assosiations. (Seligman)
• Research Contradiction.
• Early humans didnt consume most of their calories from meat but plants. But also if they only ate plants there wouldnt have eaten sufficient calories to survive. (Cordian)
• Not all food preferences come from evolution because the EEA says that most of the calories come from meats and as science has shown meats can cause cholesterol.

• Real World Application- Its been shown that our early food preference has something to do with association. Cancer patients were given ice cream prior to their chemotherapy or the therapy they were receiving, the results showed that they developed an aversion to that flavour this led to the 'scapegoat technique' (Bernstein and Webster)
• Testing evolutionary hypothesis- A common way to test the theory is by looking at chimpanzees or modern day products. However a search for an ultimate cause may lead us to miss the proximate cause such as adverts, availability and laziness.
• Cultural differences- The evolutionary approach fails to acknowlege the importance of cultural influences on our eating behaviour.