mancatul 2

Question 1

What is obesity?

Answer 1

When BMI is 20% above the ideal weight.
BMI - basic measure of body fat based on height and weight

Question 2

Is obesity a genetic problem?

Answer 2

Obesity is thought to have a strong genetic component and a smaller environmental component.

Question 3

What is the evidence that obesity has a genetic component? (From animals)

Answer 3

Animal studies
Animals are used to test the effect of lesions to specific brain areas that are important to regulate eating and satiety e.g. the lateral hypothalamus LH

LH contains receptors that pick up info from the digestive system and inhibit eating

Animals are used to see what happens when some chemicals are not produced like leptin (responsible for satiety)

Question 4

What is the evidence that obesity has a genetic component? (Twin studies)

Answer 4

5000 pairs of twins showed that a child’s risk of becoming overweight is due to nature
Genes contribute 77% of the variance

Question 5

What is the evidence that obesity has a genetic component? (Heritability of obesity)

Answer 5

Heritability of obesity: chance of being overweight

2 obese parents : 70% chance child will be obese

2 obese parent: 40%

No obese parent: 10%

Question 6

What is the evidence that obesity has a genetic component? (Adoption studies)

Answer 6

There is more similarity between adopted children and biological parents compared to adoptive parents

Question 7

1. How has the set-point theory been used to explain obesity?

Answer 7

Individuals set their eating habits along a subjective set point so that the amount of food intake and energy used is such that we reach a subjective point.

Energy levels below point - we eat
Set point reached - we will stop eating

Individuals engage in eating behaviour to maintain internal homeostasis (a constant internal state)

Obese individuals may have higher lipostatic set-point than non-obese individuals
This means obese people have a higher food intake in order to operate normally

Question 8

2. How has the role of hormones been used to explain obesity?

Answer 8

Leptin is one of the hormones that signals long-term satiety
It is secreted from fat tissue
more fat equals more leptin
More leptin equals no eating

Question 9

What is the role of leptin in obesity?

Answer 9

Lack of leptin corresponds to obesity in animals
Leptin injections are linked to weight loss in obese mice

Lack of leptin receptors causes a state of perceived constant starvation
Mice do not lose weight following leptin injections. – even if you have leptin, not having receptors means that signals do not reach the brain that you are full

Question 10

Is leptin the only cause of obesity?

Answer 10

No
Only 5-10% of obese humans have low leptin levels
Human obesity does not uniquely result from lack of adequate leptin signals

Question 11

What is the problem with genetic-based theories of obesity?

Answer 11

If obesity is mainly genetic then why is it on the rise because genes do not change so fast

Bc genes and environment interact - some high risk groups have genes that are susceptible to obesity - for those ppl the environment is critical for developing obesity

Question 12

What is the evidence that obesity is due to environment?

Answer 12

Pima indians split into 2 groups: one remained in US, one settled in Mexico

American pima have adopted the modern american lifestyle and diet

This made them 26kg heavier than mexican cousins, and it increased their cholesterol levels and diabetes – obesity came with consequences to health

Question 13

What is the Thrifty Genotype genetic and environment theory?

Answer 13

There is a predisposition to maintain higher weight

In early evolutionary history - thrifty genes were advantageous - accumulating fat was good bc this reserved fat helped them survive when there wasn’t food available

In modern world such genes are disadvantageous bc they promote fat deposition in preparation for a famine that is unlikely to come

thrifty genotype + modern diet = rising obesity

Question 14

What are the consequences of obesity?

Answer 14

Infertility
Some cancers
Diabetes
Heart diseases

Financial consequence

Stress
Anxiety
Depression
Discrimination and negative attitudes

Question 15

What is anorexia?

Answer 15

Someone tries to keep their weight as low as possible by starving or exercising excessively

Question 16

What is the prevalence of anorexia?

Answer 16

1 in 250 women
1 in 2000 men

Develops during adolescence

Question 17

What is the diagnostic criteria for anorexia?

Answer 17

Intense fear of gaining weight
Refusal to maintain weight at above or minimally normal weight for age and height

Question 18

What are the possible biological causes of anorexia?

Answer 18

A. Twin studies - 50-80% of variance in anorexia can be explained by genetic factors

B. Ghrelin (hunger) is high in anorexic people
Leptin (satiety) is low in anorexic people - satiety is never properly reached

Question 19

What are the possible psychological causes of anorexia?

Answer 19

OCD, anxiety, depression

Question 20

What are the social causes of anorexia?

Answer 20

Social isolation, family dynamics

Question 21

What is anorexia as a multi-factorial disorder?

Answer 21

There is no anorexia gene.
There are certain traits that are personality related (perfectionism, OCD, rigidity) and social factors that might predispose certain people to become anorexic.
These traits make some people more likely to want to diet.
Dieting results in weight loss which triggers neurobiological changes.
Changes might promote increase in rigidity, anxiety and depression and therefore dieting is reinforced to maintain these emotions under control.

You can come out of this cycle and 50-70% do recover from weight loss.

Question 22

What was the study conducted to see if it is possible to induce anorexia?

Answer 22

36 young men underwent very restrictive caloric intake for 6 months

After severe dieting, they developed symptoms which are similar to those experienced by those with eating disorders. Physical, psychological changes continued after rehabilitation so they were permanent.

They also increased in depression and hysteria

So these features are consequence of anorexia rather than a cause of anorexia

Question 23

What are the consequences of anorexia?

Answer 23

Brain and nerves - can’t think right, fear of gaining weight, moody
Heart: low blood pressure, slow heart rate

Sleep problems, loss of interest in people, feeling down or depressed

Question 24

What are the similarities between anorexia and obesity?

Answer 24

They both imply unbalanced eating

They both result in abnormal body weight

They are both multi-factorial disorders – result of many elements

Question 25

What are the differences between anorexia and obesity?

Answer 25

Obesity is more strongly related to genetic abnormalities than anorexia

Anorexia has a stronger emotional component

Anorexia has stronger implications for body image than obesity – anorexic patients have a body image that does not correspond to reality