EVOLUTIONARY AND ENVIRONMENTAL PERSPECTIVES ON HEALTH AND DISEAS: OBESITY AND DIABETES

Question 1

What’s the aim of evolutionary medicine?

Answer 1

to try to find evolutionary explanations for vulnerabilities to disease e.g. are there selective advantages to traits that predispose us to diseases

Question 2

explain how cystic fibrosis may be a heterozygote advantage?

Answer 2

it may have resistance to salmonella, diarrhoea from lactose intolerance and it may have resistance to cholera or tuberculosis

Question 3

what are some increased risks with obesity?

Answer 3

hypertension
coronary heart disease
certain cancers
arthritis
type 2 diabetes

Question 4

what are some causes of obesity?

Answer 4

the western high energy diet 
sleep deprivation
increase in sedentary lifestyles
genetics
pathology and endocrine disorders
proximate and evolutionary factors

Question 5

what are proximate factors?

Answer 5

causal factors- lifestyle

Question 6

what are evolutionary factors?

Answer 6

factors that influence survival e.g. genetics

Question 7

outline the anthropology of obesity?

Answer 7

Very few reports of obesity in populations with true hunting and gathering subsistence strategies
A rapid increase in prevalence of obesity in populations undergoing ‘modernization’

Question 8

what are 2 potential reasons for humans being predisposed to putting fat on?

Answer 8

natural selection and sexual selection

Question 9

how could natural selection be a cause of obesity?

Answer 9

fatter individuals may have had better survival chances and greater reproductive success.
Especially important in a feast/famine situation, for example in a seasonal environment or during long migrations.

Question 10

how could sexual selection be a cause of obesity?

Answer 10

In populations where food was traditionally scarce (e.g. Polynesia), fatness is often preferred and is associated with wealth and high social status
preferences alter over time

Question 11

describe the link between obesity and type 2 diabetes?

Answer 11

obese individuals are at a high risk of getting diabtes

Question 12

what is type 1 diabetes?

Answer 12

insulin dependant diabetes mellitus where theres damage to beta cells in the pancreas
tends to have a juvenile onset

Question 13

what is diabetes?

Answer 13

Disease of glucose metabolism defined by elevated blood sugar.

Question 14

what is type 2 diabetes?

Answer 14

non-insulin dependant diabetes mellitus which tends to have an adult onset

Question 15

what is gestational diabetes?

Answer 15

it occurs during preganncy and normally stops after pregnant but is an indicator of future diabetes risk

Question 16

what is the thrifty genotype hypothesis?

Answer 16

Genes related to type II diabetes enabled people in feast/famine environments to survive.
Rapid change of subsistence strategy led to lots of obesity and type II diabetes in populations with a feast/famine history

Question 17

what are thrifty genes?

Answer 17

genes which enable individuals to efficiently collect and process food to deposit fat during periods of food abundance in order to provide for periods of food shortage

Question 18

what is the evidence for the thrifty genotype hypothesis?

Answer 18

twin and family studies show a genetic component to type 2 diabetes
a gene associated with low body mass at birth, insulin resistance and diabetes is found in 100% of some populations in the pacific islands but less than 10% in Britain

Question 19

whats an issue with the thrifty phenotype hypothesis?

Answer 19

Would expect greater insulin resistance in colder climates due to longer winters – but what we actually see is that the highest incidence of type II in tropical populations and the lowest in colder habitats

Question 20

what is the thrifty phenotype hypothesis?

Answer 20

the epidemiological associations between poor fetal and infant growth and the subsequent development of type 2 diabetes and the metabolic syndrome result from the effects of poor nutrition in early life, which produces permanent changes in glucose-insulin metabolism

Question 21

whats some evidence for the thrifty phenotype hypothesis?

Answer 21

the dutch hunger winter shows that undernutrition in utero leads to impaired glucose tolerance and type II diabetes.
The diabetic twin also had a significantly lower body mass at birth.
Rats with restricted nutrition in utero had worse glucose tolerance in late maturity than rats that had experienced normal fetal nutrition.
Improved maternal nutrition over a number of generations will lead to the reduction of type II diabetes rates: this change may be occurring in populations in Nauru in the Pacific.

Question 22

whats some issues with the thrifty phenotype hypothesis?

Answer 22

No hard evidence that low body mass at birth is related directly to maternal nutrition.
The theory works better for males than for females

Question 23

how does the thrifty genotype explain gout?

Answer 23

Gene for uricase synthesis is faulty in all primates and defunct in great apes. this means excess uric acid cant be broken down in apes which promotes the build up of fat which increases chances of survival through the winter