A study in twins reveals how genetic factors make some girls more prone to buying into society's fascination with thinness -- and therefore more at risk of developing eating disorders.
PROBLEM: We often (justifiably) blame media and general societal attitudes for the prevalence of eating disorders in Western culture. But why is it that some women strongly subscribe to the ideal of thinness endorsed by airbrushed photographs and stick-thin celebrities -- the first step down the path to body dissatisfaction and the ultimate possibility of developing anorexia, bulimia, or just an unhealthily preoccupation with weight -- while others seem immune?
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METHODOLOGY: In order to parse out the roles of genetic and environmental factors in the internalization of these attitudes, researchers interviewed over 300 female twins, aged 12 to 22, and used a standardized scale to determine the degree to which each girl desired to look like people from magazines, movies, and television. Then, controlling for age and BMI, they compared the genetically identical, monozygotic twins to the dizygotic twins, who only share half of their genes.
RESULTS: The identical twins were more similar to one another in their internalization of the thin ideal than were the fraternal twins, but all pairs of siblings, despite growing up in similar environments, differed from one another in the extent to which they desired thinness.
CONCLUSION: Over 40 percent of the desire to be thin can be attributed to genetics. General environmental factors have no measurable effect on the internalization of the thin ideal, but nonshared environmental factors -- those that each sibling experiences individually -- significantly influence it.