Waist-hip ratio

Waist-hip ratio or Waist-to-hip ratio (WHR) is the ratio of the circumference of the waist to that of the hips. It is calculated by measuring the waist circumference (located just above the upper hip bone) and dividing by the hip circumference at its widest part (waist/hip). The concept and significance of WHR was first theorized by evolutionary psychologist Dr. Devendra Singh at the University of Texas at Austin in 1993.

Health
A WHR of 0.7 for women and 0.9 for men have been shown to correlate strongly with general health and fertility. Women within the 0.7 range have optimal levels of estrogen and are less susceptible to major diseases such as diabetes, cardiovascular disorders and ovarian cancers. Men with WHRs around 0.9, similarly, have been shown to be more healthy and fertile with less prostate cancer and testicular cancer.

WHR has been found to be a more efficient predictor of mortality in older people than waist circumference or body mass index (BMI). If obesity is redefined using WHR instead of BMI, the proportion of people categorized as at risk of heart attack worldwide increases threefold.

Other studies have found waist circumference, not WHR, to be a good indicator of cardiovascular risk factors, body fat distribution, and hypertension in type 2 diabetes.

Attractiveness
Scientists have discovered that the waist-hip ratio (WHR) is a significant factor in judging female attractiveness. Women with a 0.7 WHR (waist circumference that is 70% of the hip circumference) are usually rated as more attractive by men from European cultures. Such diverse beauty icons as Marilyn Monroe, Sophia Loren, Gong Li, and even the Venus de Milo all have ratios around 0.7, even though they have different weights. In other cultures, preferences appear to vary according to some studies, ranging from 0.6 in China, to 0.8 or 0.9 in parts of South America and Africa,  and divergent preferences based on ethnicity, rather than nationality, have also been noted.

Note: In the studies referenced above, only frontal WHR preferences differed significantly among racial and cultural groups. When actual (circumferential) measurements were made, the preferred WHR tended toward the expected value of 0.7 universally. The apparent differences are most likely due to the different body fat storage patterns in different population groups. For example, women of African descent tend to store their fat in their buttocks more than women of other groups. Therefore, their WHR as viewed from the front may appear to be much greater than when viewed from the side. The inverse may be true of women of East Asian ancestry. Therefore, African men appear to value a woman's small WHR in profile and an Asian men may place more value on an exaggerated frontal WHR compared to European men.

Intelligence
Women with a low waist-hip ratio have been shown in studies to be smarter and have smarter offspring. Using data from the U.S. National Center for Health Statistics, William Lassek at the University of Pittsburgh in Pennsylvania and Steven Gaulin of the University of California, Santa Barbara, found a child's performance in cognition tests was linked to their mother's waist-hip ratio, a proxy for how much fat she stores on her hips.

Children whose mothers had wide hips and a low waist-hip ratio scored highest, leading Lassek and Gaulin to suggest that fetuses benefit from hip fat that contains polyunsaturated fatty acids critical for the development of the fetus's brain.

Artificial alteration
Many methods have been used to artificially alter a person's apparent WHR. These include corsets used to reduce the waist size and hip and buttock padding used by some transgendered people to increase the apparent size of the hips and buttocks.