Even women who are confident about their bodies have an internalized desire to be a certain size and shape.
Subconsciously, even confident women may be concerned about their weight.
More women than expected might be on the edge of an eating disorder.
For women, body image is wrapped up with cultural ideals of beauty.
To be an American woman and feel good about your body requires a powerful inner strength and the will to resist an unrealistically skinny social ideal.
But even women who truly accept themselves as they are have internalized the desire to be thin, suggests a new study that looked deep into women's brains. The study found that the brains of healthy women resemble those of bulimic women when confronted with the idea that they might be overweight.
The findings might eventually help doctors better evaluate and treat body image issues, no matter how subtle.
"This is kind of validating the suspicion that most women are teetering on the edge of an eating disorder," said Mark Allen, a neuroscientist at Brigham Young University in Provo, Utah. "If the brain response is so strong in these apparently healthy women, maybe most of us could use a little dose of what it is that you go through in an eating disorder therapy."
Who are you? What makes you unique? What fulfills you? Are you friendly, cheerful, grumpy or important? When people consider questions like these that force them to engage in serious self-reflection, activity picks up in a part of the brain called the medial prefrontal cortex.
Scientists have suspected that this self-reflective part of the brain could betray subconscious thoughts that people might not even know they have. For example, other studies have shown that, in tasks like word-associations, people who don't think they're racist still show racist tendencies when they don't have time to consciously override what's under the surface.
Allen and colleagues looked into hidden feelings about body image by using fMRI machines to scan the brains of 10 healthy women. The women were thin, but all had passed eating disorder screening tests with flying colors. So, theoretically, they felt just fine with their bodies.
While hooked up to brain scanners, the women looked at images of avatar-like models in skimpy bikinis: some overweight, some skinny. With each image, the women were told to imagine that someone else was saying the model looked like her.
When overweight images popped up, the medial prefrontal cortex lit up in all of the women, the scientists reported in the journal Personality and Individual Differences. Simply imagining that they might be overweight seemed to make the women question their sense of self, even though they claimed afterward that the test was boring or meaningless.
"Women are actually engaging in an evaluation of who they are and whether they are worthwhile as a person," Allen said. "Even though women might claim to be well adjusted and not care about body issues, subconsciously they might care."
Based on the new results, it now appears that there is a finer line between women with and without eating disorders than scientists previously suspected, Allen said. Their brains aren't exactly the same: Bulimic women had stronger reactions in their medial prefrontal cortexes as well as activity in a part of the brain that processes negative emotions.
But most men showed no response at all to pictures of other men in bathing suits, either fat or thin. (Bodybuilders were an exception.)
As brain-scanning technologies become cheaper and more accessible, the results might give doctors new tools for figuring out when women need counseling and how likely their eating disorders are to relapse. At the very least, the new work helps validate what women go through in our society day after day, said Greg Siegle, a neuroscientist at the University of Pittsburgh School of Medicine.
"Something is happening for women with regard to shape and weight, and that's for real," he said. "This study is showing it at a biological level. It's not just a myth."