Biological Explanations Of Obesity

Question 1

Describe the genetic explanation for obesity.

Answer 1

Inherited due to evolutionary survival advantage. Suggests there is a thrifty gene which allows people to make the most efficient use of food intake and store the rest as fat. Would have been adaptive before as people w the gene can survive food shortages. Research has found that obesity is polygenic w 97 genes associated w 2.7% variation in BMI.

Question 2

Evaluate the genetic explanation for obesity.

Answer 2

S - meta analysis of 8000 MZ and 10000 DZ twins showed a 60-80% concordance. 540 adults adopted showed similarity in weight category to biological parents not adopted.
C - suggests most people would’ve inherited it if it aided survival so most people should be obese. Only been increase in obesity rates recently in some cultures. Twin studies unreliable.

Question 3

Describe serotonin as a neural explanation for obesity.

Answer 3

Dopamine usually stimulates areas of the brain producing feelings of satisfaction and pleasure, including pleasure from eating and eating cues. Theory suggests obesity is associated with dysfunctional dopamine systems. Insufficient dopamine = pleasure feelings wont be sent. One exp is a shortage of D2 dopamine receptors in the brain. Eat more to feel pleasure

Question 4

Evaluate dopamine as a neural explanation for obesity.

Answer 4

S - obese people produce leptin but it doesn’t suppress hunger / don’t produce it at all. Other research found obese people have a poorly functioning dersal stratium leading to reduced dopamine signals. Gene studies found DRD2 gene that codes for D2 receptors in the striatum using Pet scans - one version of the gene = 30-40% less dopamine receptors compared to those who have other versions.

Question 5

Describe serotonin as a neural explanation for obesity.

Answer 5

Low serotonin levels argued to be implicated. Serotonin signals to the VMH when sufficient food is consumed leading to stopping eating. When serotonin is low, inaccurate satiety signals are sent to the VMH so overeating occurs.

Question 6

Evaluate serotonin as a neural explanation for obesity.

Answer 6

S - mice who were genetically engineered to have no 2C serotonin acceptors showed late onset obesity

Question 7

Generally evaluate neural explanations for obesity

Answer 7

C - alternative explanations, can’t extrapolate from animal studies
I - determinism
P - SSRIs, drug therapies, leptin replacement therapies