Many factors have been blamed for women's desire to be thin: Barbie dolls, models in magazines, cultural expectations at large. These factors may all hold a part of the blame, but why is it that some women - and men - see such images and start critiquing their own bodies, while other people seem to be immune? And, while most of society is exposed to the same images, why is it that relatively few people develop eating disorders? A study published in the International Journal of Eating Disorder proclaims that the answer may lie in genetics.

"We're all bombarded daily with messages extoling the virtues of being thin, yet intriguingly only some women develop what we term thin ideal internalization," Jessica Suisman, a researcher at Michigan State University, said in a statement.

The study, conducted by Suisman and her colleagues, examined nearly 350 twins. All were women between the ages of 12 and 22, and 80 percent of participants were Caucasian.

The team gave the participants a questionnaire that assessed their body image, how much they wanted to be thin, and wanted to look like celebrities. The test is comprised of questions like "I've felt pressure from TV or magazines to exercise" and "I wish I looked as athletic as sports stars." Once researchers determined the participants' level of thin idealization, they compared identical twins, who share 100 percent of their genes, and fraternal twins, which share 50 percent. They also asked about shared and non-shared environmental factors. Shared environmental factors included parents and living in the same home, while non-shared environmental factors included one twin being involved in an activity in which weight is important, like dance or gymnastics.

The study found that identical twins had more similarly aligned levels of thin idealization than fraternal twins had. Researchers estimate that as much as 43 percent of thin idealization comes from genetics. They say that no particular gene is likely to blame, but rather a combination of certain genes interacting.

"The broad cultural risk factors that we thought were most influential in the development of thin-ideal internalization are not as important as genetic risk and environmental risk factors that are specific and unique to each twin," Suisman said.

Suisman advises women who believe that they idealize thinness to try to avoid negative thoughts about their bodies. She says that it may also help to be in social and leisure environments that do not emphasize the importance of being lean. The researchers hope to look in the future at what "underpins" the genetic influence on thin idealization. They also hope to have a more ethnically and culturally diverse sample of women to examine.