New research casts doubt on the claim that women who are thin and curvy are found attractive because they are healthy and fertile.

Men tend to be most attracted to women with a relatively low waist-to-hip ratio (WHR) of about 0.7 and a body mass index (BMI) around 20 or below. Researchers have theorized that shapeliness and thinness in women are found attractive because they are markers of fertility and health.

But two new studies published in Evolutionary Psychology have failed to find evidence to support this theory — and found some evidence that directly contradicts it.

“It has been widely accepted among evolutionary psychologists that men are attracted to women with maximal fertility, but the evidence that was used to support this idea seemed weak,” said study author William D. Lassek of the University of California at Santa Barbara.

The researchers reviewed previous studies on the topic, but failed to find any evidence that supported the view that low WHRs and low BMIs were associated with better fertility. Instead, they found that both low WHRs and low BMIs were linked to reduced fertility.

Data from 3,164 American women who participated in the first National Health and Nutrition Examination Survey also showed that women with low BMIs in early adulthood had fewer subsequent live births compared to those with higher youth BMIs.

In a separate study, the researchers examined data from 5,076 American women who participated in the third National Health and Nutrition Examination Survey. But they found that women with low BMIs or smaller waist sizes did not tend to have better overall health.

“Science progresses because even views which most scientists accept are still subject to criticism and testing. Although it makes sense that men would want mates with high fertility, the evidence does not support this,” Lassek told PsyPost.

“Women with features that are judged attractive (in groups with plenty of food), like a low body mass index, actually have lower fertility and a greater likelihood of having a newborn who does not survive.”

“Another explanation for why men are attracted to women with low waist-hip ratios and low BMIs needs to be found. One possibility is that men prefer young women even though they are less fertile,” Lassek added.

The studies, “Do the Low WHRs and BMIs Judged Most Attractive Indicate Higher Fertility?” and “Do the Low WHRs and BMIs Judged Most Attractive Indicate Better Health?“, were authored by William D. Lassek and Steven J. C. Gaulin.