Biological Explenations For Obesity

Question 1

What are the genetic explanations for obesity

Answer 1

-genetic concordance rates
-polygenic determination

Question 2

What are the neural explanations for obesity

Answer 2

-Low serotonin
-Low serotonin

Question 3

Obesity runs in families- concordance rates

Answer 3

-Concordance rates for first degree relatives who love together is 20-50%
-Nan, meta analysis of 12 twin studies and found concordance rates of 61-80% for MZ twins

Question 4

Polygenic determination

Answer 4

-Locke studied 300,000 people and identified 97 genes which are associated with high BMI
- Gene action on obesity is polygenic
-There is no one single cause for obesity
-Watson thinks that as many as 400 genes are involved

Question 5

Low serotonin

Answer 5

-Abnormally low levels of serotonin can occur due to stress / comorbid disorders like depression / genetic inheritance
-This creates inaccurate satiety signals that are sent to the hypothalamus, disinhibiting eating behaviour
-It also leads to cravings for carbs, energy dense foods, causing weight gain

Question 6

Low dopamine

Answer 6

-Dopamine is derived from the pleasure we associate with eating
-Wang found that obese individuals had lower dopamine D2 receptors compared to normal weight participants in the striatum (brains reward system)
-Dopamine cannot perform it’s pleasurable reward if it’s too low so a person does not feel good after eating
-So they overeat to attempt to activate the reward centres which provide the feeling of pleasure

Question 7

Normal serotonin

Answer 7

-Normal levels of serotonin regulate eating behaviour by inhibiting the activity of areas in the hypothalamus and the ventromedial hypothalamus, signaling that we’ve eaten to satiety

Question 8

Normal dopamine

Answer 8

-Normal levels of dopamine stimulate areas of the brain such as the hypothalamus, hippocampus and amygdala to provide rewarding feelings of pleasure
-Dopamine is derived from the pleasure we associate with eating

Question 9

Supporting evidence for serotonin

Answer 9

-Ohia
-Highlights the importance of the 2C serotonin receptor
-‘knockout mice’ were genetically engineered to have no functioning 2C receptors and developed late-onset obesity

Question 10

Contradictory evidence for genetics

Answer 10

-Parachinni
-Meta analysis of 25 studies investigating genes that impact the role of leptin and leptin receptors
-Low leptin levels lead to obesity due to causing feelings of hunger
-Researchers found no link between these genes and obesity
-Role of leptin does not have a purely genetic basis, human beings are more complex

Question 11

Extra PEELs

Answer 11

-Shared environments assumption
-Biologically deterministic

Question 12

Practical applications, neural and genetic

Answer 12

-Treatments that correct the levels of serotonin and dopamine ie. SSRI’s
-Personalised medicine with drugs tailored for someone’s genetic profile
-Educated on the biological aspects
-Improves QoL by reducing mortality risks