biological explanations for eating behaviour

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neural mechanisms


  • controls and maintians the internal state, a time lag between the mechanisms restoring the state and the body registering the effect

lateral hypothalamus

  • controls the initiation of eating, glucose levels fall activating feelings of hunger
  • rats with damaged LH stopped eating (aphagia) and starved, stimulation of LH caused eating. neurotransmitter neuropeptid Y when injected into rats caused eating even after satiety

ventromedial hypothalamus

  • stops eating, glucose levels rise causing feelings of satiety
  • rats with damage to the VMH showed hyperphagia and ate until over weight, when starved and then allowed to eat the rats ate to maintain the obese weight
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neural mechanisms evaluation

  • inorder for hunger to be adaptive food should be found before energy depletes
  • neuropeptid Y could explain why obese people find is difficult to stop eating, it is also produced by abdominal fat leading to hunger leading to more fat - a circle of weight gain
  • neural circuits are thought to control eating not just the hypothalamus
  • if the rats with hyperphagia had to work for their food then they would not eat as much, a study has shown this for humans too- those who had to crack almonds who not eat as many
  • ghrelin hormone is secreted in response to stress reducing anxiety and increasing appetite
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evolutionary explanations

preference for sweet food

  • a sign of ripeness in fruit- high sugar, a good sorce of energy and calories
  • sweet berries are rarely poisonous, bitter tastes are associated with poisonous foods  

preference for high fat

  • fats have high amount of calories, leading to better food reserves
  • bingeing on fats would be advcantagous when food supply is short 

preference for meat

  • meat was good to ancestors as high in nutrients, anabled brain development that would not have been possible when eating plants 

Evaluation- 3 day old babies prefer sweet liquids, adaptive for breast milk to be sweet 

- starving chimps ate the fattiest meats first because of the calorie content

- evidence suggests sweet foods are preferred because of the calorie content  

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