biological epxlantions for obseity Flashcards
genetic explanation for obesity
obesity runs in families
looks to family studies for evidence
clear family related patterns to obesity - measured in terms of BMI
caution is needed when interpreting finings because of the difficulty separating genetic anf environmental influences
concordance rates for first degree relatives are 20-50% which indicates a moderate degree of heritability
twin studies - greater genetic component
Nan et al - meta analysis of 12 twin studies involving 8000 MZ and 10000 DZ
concordance rates 61% to 80% - demonstrates a substiantial genetic cononeny
polygenic determination
Locke et al
studied genomes of 300000 people and identified 97 genes associated with variations in BMI
demonstrates that the actions of genes on obesity is polygenic
genetic inheritance involves multiple genes - effects interacting with each other
different genes may influence different aspects of obesity
no single genetic cause of obesity
locke - 97 genes accounted for only 2.7% of BMI variation - small fraction of heritability of obesity
neural explanations for obesity
focuses on neurotransmitters
serotonin anf dopamine
partially in terms of their role in the brains reward systems
serotonin
most research for humans andf non humans show that obesity is associated with abnormally low leeks of serotonin
normal levels of serotonin regulate feeding behaviour by inhibiting the activity of various sites int he hypothalamus - ventromedial hypothalamus
serotonin tsugnals tot he hypothalamus that we have eaten to satiety
dysfunctions in the serotonin system can occur due to stress or co-morbid disorders such as depression
may even be genetically inherited
levels of serotonin are a born ally low creating inaccurate satiety signals that are sent to the hypothalamus
disinhibiting eatign behaviour
low serotonin levels lead to cravings for carbohydrates energy dense foods causing weight gain through oo many calories
dopamine
crucial role in the brian’s reward and motivation systems
normal levels of neurotransmitter stimulate the brain areas such as the hypothalamus - hippocampus - amygdala
provides rewarding feelings of pleasure and wellbeing
dopamine activity is associated with pleasure we derive from eatign and cues associated with eating
Wang et al - found that obses indouals had significantly fewer dopamine d2 receptors than normal weight control in the striatum
cannot perform its usual pleasurable reward function in response to eatig - person does not feel good after eating
overeating can hen be seen as an attempt to activate reward centres in the brian that provide feelings of pleasure and wellbeing
suggest that obesity is the outcome of a food addiction that operated neurochemically
evaluation for genetic - strenght
research support for genetic explanations - twin studies and family studies
high concordance rates 20-50% suggest a high genetic influence
ev;actions for genetic - limitation
diathesis stress model - other explanations
environmental factors are also importnat
trigger the diathesis
stressors
evaluation for genetic - limitation
assumptions of the dame environment for twins
evaluation for neural - strength
research support
Ohia et al
2c receptors importance in obesity
knockout mice studies were reviewed
animals were genetically engineered to have no functioning 2c receptors because the gene is removed /knwocked out
findings shows that mice develop late onset obesity
supports the link between obesity and syfcutnional serotonin systems
evaluation for neural - strenght
application
neural explanations lead to drug treatments for obesity
aims to increase levels for serotonin and dopamine
altering satiety signals helping to prevent disinhibition eating
understanding of neural activity coul lead to better drug treatments for obesity
