When Viren Swami, Ph.D., started his graduate work in psychology, he happened upon the Venus de Milo at Paris’s Louvre Museum. He was struck by her imperfections. “It’s not symmetrical; she’s cracked all over the place,” he says. “She’s missing a foot.” (Not to mention both of her arms.) The Venus de Milo wasn’t always revered, Swami submits—but today she is. What he took from the sculpture’s history: Our beauty ideals are not set in stone.

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It’s a fitting metaphor for Swami’s work. A Reader in Psychology at the University of Westminster in London and YouBeauty Attraction Expert, Swami has hit upon this concept in dozens of studies focused on cross-cultural standards of attractiveness.

“One of the things I’m interested in is how these ideas are really malleable,” Swami says. “They’re not fixed in time, they’re not fixed in place.”

While earning his undergraduate degree in psychology at University College London, Swami first became interested in the way cultures’ beauty standards evolve. In his doctorate work at the same school, he honed in on the range of factors that influence which body types we find attractive, such as media, upbringing and even our current mental state.

As lead author of “The International Body Project,” published in 2010 in The Personality and Social Psychology Bulletin, Swami, his colleague, David Frederick, and an international team of researchers surveyed more than 7,400 people in 26 countries about their concept of the ideal female form. Among most of the sites—socioeconomically-developed, urban areas, including Los Angeles, Toronto, London and Melbourne—differences in body weight preferences were minor. No big shock: Men and women alike found a slender physique most attractive. But in poor regions of Malaysia and South Africa, people far favored heavier figures.

“Body fat is acting as an indicator of status,” Swami theorizes. In poor, rural areas, the richer you are, the more likely you are to be heavy, since you can afford to buy more food and avoid working with your hands. The opposite might be true in urban areas, where money begets a gym membership and organic vegetables.

The pattern held true within cultures, as well. There was a fairly uniform preference for heavier figures among groups of lower socioeconomic status, and for thinner figures among groups of higher socioeconomic status.

MORE: Workouts for Your Body ShapeSome of Swami’s earlier work comparing beauty ideals in the U.K. and South Africa support the resources explanation. In a 2006 study, he and his colleagues found that Zulus in KwaZulu-Natal, South Africa valued relatively overweight women, whereas white, U.K. respondents didn’t. At the time, 56 percent of rural South Africans reported growing hungry, and the population was rife with meningitis, Tuberculosis, HIV and AIDS. Emaciation is the most visible symptom of these diseases, so picking an overweight mate, Swami says, could help narrow the chances of infection.

But these things aren’t immutable: Zulus who moved to England adopted European ideals within a year and a half of leaving Africa.

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In “The International Body Project,” Swami and his collaborators measured women’s satisfaction with their own bodies. By and large, women in high socioeconomic societies wished they were thinner. (Women in the Americas were the most dissatisfied with their bodies.) Meanwhile, rural women in impoverished states, where extra meat on the bones is associated with health and fertility, tended to be more satisfied with their bodies. With the exception of East Asia, men everywhere idealized heavier female bodies than women did, and women assumed men liked thinner figures than they actually did.

Many women can appreciate that we’re generally hard on ourselves when it comes to body image, especially when we’re bombarded with the media’s portrayal of thinness and beauty. And while sweeping cultural biases pervade, certain subcultures have their own standards and sensitivities. For instance, Swami found that female contemporary dancers had much more positive views of their bodies than ballet dancers, which he attributes to the way they use and appreciate their bodies. Contemporary dancing isn’t rigid and uniform, the way ballet is. Beyond this, contemporary dancers’ body image improved along with their skill, while the opposite was true for ballet dancers.

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Beauty ideals can even vary from moment to moment. In two separate studies, Swami found that men who were stressed and men who were hungry both had increased preference for heavier women. Again, this is likely linked to resources. A stressed or hungry person might be drawn to a mate who looks like she can fend for herself, not one who needs protection.

Does that mean heavy women should seek out starved companions? Not so much, says Swami, who prefers to draw a larger conclusion: “People think these ideals are fixed, and you can’t change them. But our results suggest that’s not the case.”

And if they’re changeable, perhaps we can change them for the better.  “We should initiate a debate about the impact of an excessive focus on appearance,” he says. “We could begin to promote positive body image by teaching schoolchildren how to respect their bodies and provide them with the tools they need to critically evaluate what they see in the media. Everyone can be beautiful to someone else. And I like that message.”

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