AQA A2 Psychology Unit 3 Eating Behaviour: Biological Explanations And Evolutionary Explanations Of Obesity Notes

A2 Psychology Unit 3 Eating Behaviour: Biological Explanations And Evolutionary Explanations Of Obesity Notes

What You Need To Know:

·  Biological explanations for one eating disorder: obesity

Genetics:

People react to food in different ways (e.g. store more energy as fat) and this may be due to genetic variations.

Twin studies

·  Evidence suggests that obesity often runs in families.

·  Bouchard et al (1990) overfed 12 pairs of male MZ twins and found three times more similarity of weight gain within pairs than between pairs, strongly indicating genetic factors.

·  Stunkard et al (1990) estimated from studies of 25,000 pairs of twins that male identical twins reared apart had a BMI estimated at 70% heritable for males and 66% for females.

·  Price and Gottesman (1991) found that body fat of identical twins reared apart correlated at 0.61 whilst that of identical twins reared together was 0.75. Being reared apart had little impact on heritability, emphasising the role of genes.

Adoption studies

·  Adoptive parents and children do not share genetic material but share a common environment. If obesity is genetic then there should be more similarity with biological than adoptive parents.

Stunkard et al (1986) - Adoption studies and obesity

Method: The weight of 540 adult adoptees from Denmark was compared with that of both their biological and adoptive parents. The adoptees were split into 4 weight classes - thin, median, overweight and obese.

Results: There was a strong relationship between the weight of the adoptees and that of their biological parents. There was no relationship between the weight of the adoptees and their adoptive parents in any of the weight classes.

Conclusion: Genetic influences have an important role in determining adult weight, whereas environment seems to have little effect.

Evaluation: This finding is supported by other biological versus adoptive relative research and even by some twin studies. However, it's probably too reductionist to say that genetics alone are responsible for obesity. Also, the participants were all from Denmark, so the results can't be generalised to the whole population.

Montague et al (1997) - Leptin's role in obesity

Method: Two severely obese children (male and female cousins) were studied - a large proportion of their total body weight was made up of adipose (fatty) tissue.

Results: A mutation on…