EVOLUTIONARY AND ENVIRONMENTAL PERSPECTIVES ON HEALTH AND DISEAS: OBESITY AND DIABETES Flashcards
What’s the aim of evolutionary medicine?
to try to find evolutionary explanations for vulnerabilities to disease e.g. are there selective advantages to traits that predispose us to diseases
explain how cystic fibrosis may be a heterozygote advantage?
it may have resistance to salmonella, diarrhoea from lactose intolerance and it may have resistance to cholera or tuberculosis
what are some increased risks with obesity?
hypertension coronary heart disease certain cancers arthritis type 2 diabetes
what are some causes of obesity?
the western high energy diet sleep deprivation increase in sedentary lifestyles genetics pathology and endocrine disorders proximate and evolutionary factors
what are proximate factors?
causal factors- lifestyle
what are evolutionary factors?
factors that influence survival e.g. genetics
outline the anthropology of obesity?
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’
what are 2 potential reasons for humans being predisposed to putting fat on?
natural selection and sexual selection
how could natural selection be a cause of obesity?
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.
how could sexual selection be a cause of obesity?
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
describe the link between obesity and type 2 diabetes?
obese individuals are at a high risk of getting diabtes
what is type 1 diabetes?
insulin dependant diabetes mellitus where theres damage to beta cells in the pancreas
tends to have a juvenile onset
what is diabetes?
Disease of glucose metabolism defined by elevated blood sugar.
what is type 2 diabetes?
non-insulin dependant diabetes mellitus which tends to have an adult onset
what is gestational diabetes?
it occurs during preganncy and normally stops after pregnant but is an indicator of future diabetes risk
what is the thrifty genotype hypothesis?
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
what are thrifty genes?
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
what is the evidence for the thrifty genotype hypothesis?
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
whats an issue with the thrifty phenotype hypothesis?
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
what is the thrifty phenotype hypothesis?
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
whats some evidence for the thrifty phenotype hypothesis?
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.
whats some issues with the thrifty phenotype hypothesis?
No hard evidence that low body mass at birth is related directly to maternal nutrition.
The theory works better for males than for females
how does the thrifty genotype explain gout?
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
