Waist–hip ratio

s at right. WHO protocol According to the World Health Organization's data gathering protocol, the waist circumference should be measured at the midpoint between the lower margin of the last palpable ribs and the top of the iliac crest, using a stretch-resistant tape that provides constant tension. Hip circumference should be measured around the widest portion of the buttocks, with the tape parallel to the floor. Practical measurement The layperson's measurement of hip circumference is the same as the WHO protocol: measure at the widest part of the buttocks or hip. There are several possible alternative definitions of waist circumference with easier-to-locate landmarks: • Waist measurements are usually obtained by laypersons by measuring around the waist at the navel, but research has shown that these measurements may underestimate the true waist circumference. • The NIH NHANES study measures at the top of the iliac crest, which is low but relatively easy to find. ==Indicator of health==

Serious health conditions The WHR has been used as an indicator or measure of health, and as a risk factor for developing serious health conditions. WHR is used as a measurement of obesity, which in turn is a possible indicator of other more serious health conditions. The WHO states that abdominal obesity is defined as a waist–hip ratio above 0.90 for males and above 0.85 for females, or a body mass index (BMI) above 30.0. WHR has been found to be a more efficient predictor of mortality in older people (>75 years of age) than waist circumference or BMI. If obesity is redefined using WHR instead of BMI, the proportion of people categorized as at risk of heart attack worldwide increases threefold. WHR may be less accurate in individuals with a BMI of 35 or higher, and more complex to interpret since an increased WHR may result from increased abdominal fat or decreased lean muscle mass around the hips. The body fat percentage is considered to be an even more accurate measure of relative weight. Of these three measurements, only the waist–hip ratio takes account of the differences in body structure. Hence, it is possible for two people of the same sex to have different body mass indices but the same waist–hip ratio, or to have the same body mass index but different waist–hip ratios. WHR has been shown to be a better predictor of cardiovascular disease than simple waist circumference and body-mass index. The study by American Heart Association has shown that measuring waistline and comparing it to hip size might be a better way to predict heart disease risk than a widely used body mass index. However, other studies have found waist circumference (particularly waist-to-height ratio) to be a better indicator of cardiovascular risk factors than the waist–hip ratio, body fat distribution, and hypertension in type 2 diabetes. Stress The stress hormone cortisol is regulated by the hypothalamic-pituitary-adrenal (HPA) axis and has been associated with higher levels of abdominal fat and therefore a higher WHR. Abdominal fat is a marker of visceral fat (stored around important internal organs such as the liver, pancreas and intestines) and has greater blood flow and more receptors for cortisol than peripheral fat. The greater the number of cortisol receptors, the more sensitive the visceral fat tissue is to cortisol. This heightened sensitivity to cortisol stimulates fat cells to further increase in size. Women who have a combination of normal BMI and high WHR experience elevated cortisol reactivity to acute stressors and failure to habituate to repeated stressors, compared to women with normal WHR. This suggests that high WHR might also indicate HPA-axis dysregulation and over-exposure to cortisol. Evidence for the relationship between cortisol and central fat distribution has primarily been studied in individuals with Cushing's syndrome. This is characterized by over-exposure to cortisol due to elevated activity of the HPA axis. A primary component of Cushing's syndrome is the accumulation of fat in the abdominal region, and it is hypothesized that elevated cortisol levels contribute to this accumulation. However, this hypothesis remains contested as cortisol levels only modestly explain variation in central fat distribution. It is more likely that a complex set of biological and neuroendocrine pathways related to cortisol secretion contribute to central adiposity, such as leptin, neuropeptide y, corticotropin releasing factor and the sympathetic nervous system. Adults with untreated congenital isolated growth hormone deficiency have increased WHRs, possibly from increased cortisone–cortisol ratios and insulin sensitivities. Sex characteristics Males with congenital adrenal hyperplasia, determined by CYP21A2 mutations, have increased WHRs. Fertility Women with high WHR (0.80 or higher) have significantly lower pregnancy rates than women with lower WHRs (0.70–0.79), independent of their BMIs. Men with WHRs around 0.9, similarly, have been shown to be more healthy and fertile with less prostate cancer and testicular cancer. One of the factors that affects a woman's waist-hip ratio is her gynoid fat distribution, a store of energy to be expended in the nurturing of offspring, both to provide adequate energy resources during pregnancy and for the infant during the stage in which they are breastfeeding. In an ancestral environment where food was scarce, a female with high levels of gynoid fat would be signalling that she in an optimal state for reproduction and nurturing of offspring. This can be seen in the fact that a female's waist–hip ratio is at its optimal minimum during times of peak fertility—late adolescence and early adulthood, before increasing later in life. As a female's capacity for reproduction comes to an end, the fat distribution within the female body begins a transition from the gynoid type to more of an android type distribution. This is evidenced by the percentages of android fat being far higher in post-menopausal than pre-menopausal women. Evidence suggests that WHR is an accurate somatic indicator of reproductive endocrinological status and long-term health risk. Among girls with identical body weights, those with lower WHRs show earlier pubertal endocrine activity, as measured by high levels of lutenizing hormone and follicle-stimulating hormone, as well as sex steroid (estradiol) activity. A Dutch prospective study on outcome in an artificial insemination program provides evidence for the role of WHR and fecundity. These investigators report that a 0.1 unit increase in WHR decreases the probability of conception per cycle by 30% after adjustment for age, obesity, reasons for artificial insemination, cycle length and regularity, smoking, and parity. Menopause, the natural or surgical cessation of the menstrual cycle, is due to an overall decrease in ovarian production of the hormones estradiol and progesterone. These hormonal changes are also associated with an increase in WHR independent of increases in body mass. Significantly, studies find that large premenopausal WHRs are associated with lower estradiol levels and variation in age of menopause onset. Circulating estrogen preferentially stores lipid deposits in the gluteofemoral region, including the buttocks and thighs, and evidence suggests that menopause-associated estrogen deficiency results in an accumulation of adipose deposits around the abdomen. These menopause-induced changes in body fat distribution can be counteracted with hormone replacement therapy. In contrast, aging males gradually accumulate abdominal fat, and hence increased WHR, in parallel with declining androgen levels. 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, which contains long chain polyunsaturated fatty acids, critical for the development of the fetus's brain. In addition, evidence suggests that children of low-WHR teens were protected from the cognitive deficits often associated with teen birth. Offspring newborn size A higher WHR corresponds to a heavier baby with a longer body and a bigger head at birth. ==Human genetics==

Studies in twins have suggested that between 22% and 61% of variability in waist-to-hip ratio may be accounted for by genetic factors. ==As an indicator of attractiveness==

Female . The earliest known representations of female figures date from 23,000 to 25,000 years ago and had bodies with vestigial head and limbs, noted for their very high waist–hip ratio of 1:1 or more. The concept and significance of WHR as an indicator of attractiveness was first theorized by evolutionary psychologist Devendra Singh at the University of Texas at Austin in 1993. Singh argued that the WHR was a more consistent estrogen marker than the bust–waist ratio (BWR) studied at King's College, London by Glenn Wilson in the 1970s. Some researchers have found that the waist–hip ratio is a significant measure of female attractiveness. Women with a 0.7 WHR are usually rated as more attractive by men from various cultures. Preferences may vary, according to some studies, to 0.8 in Cameroon and among the Hadza tribe of Tanzania, with divergent preferences according to the ethnicity of the observed being noted. In ancient Greek and Egyptian sculptures, idealized female representations typically displayed ratios of 0.7, while in Indian and African artwork, the WHRs for female statues are even smaller, at 0.6 and 0.5 respectively. It appears that men in westernized societies are more influenced by female waist size than hip size: "Hip size indicates pelvic size and the amount of additional fat storage that can be used as a source of energy. Waist size conveys information such as current reproductive status or health status ... in westernized societies with no risk of seasonal lack of food, the waist, conveying information about fecundity and health status, will be more important than hip size for assessing a female's attractiveness". By western standards, women in foraging populations have high numbers of pregnancies, high parasite loads, and high caloric dependence on fibrous foods. These variables change across cultures, suggesting that: • the normal range of female WHR was often higher than in western cultures, • what constituted locally "WHR" varied, and • average WHR of nubile females and of females of peak fertility varied. Thus, a WHR that indicates pubertal onset, sex, fertility, hormonal irregularities, and/or differentiates male from female in one population may not do so in another. In a series of 1993 studies done by Singh, men used WHR and overall body fat to determine a woman's attractiveness. In his first study, men were shown a series of 12 drawings of women with various WHRs and body fat. Drawings with normal weight and a low WHR were associated with the most positive traits (i.e. attractive, sexy, intelligent and healthy). The drawings of thin female figures were not associated with any positive traits except youthfulness. Through this study, Singh suggests that males and females may have developed innate mechanisms which detect and make use of the WHR to assess how healthy an individual is and (particularly for men), infer possible mate value. Having a healthy mate improves the chances of producing offspring with inherited genetic protection from various diseases and a healthy mate is more likely to be a good parent (Hamilton & Zuk, 1982; Thornhill, 1993). Pazhoohi et al. (2019) using eye tracking confirmed that lower than optimal WHRs when posing in contrapposto, which causes one side of the body to have a lower than optimal view-dependent WHR, are perceived more attractive and are supernormal stimuli. Furthermore, referencing a 2005 study conducted by Johnson and Tassinary looking at animated human walking stimuli, Farid Pazhoohi and James R. Liddle proposed that men do not solely use WHR to evaluate attractiveness, but also a means of sex-differentiation, with higher WHR perceived as more masculine and lower WHR as an indicator of femininity. Pazhoohi and Liddle used this idea as a possible additional explanation as to why men perceive a lower WHR as more attractive – because it relates to an expression of femininity, as opposed to masculinity and a higher WHR. On this basis, it was shown that men with lower, more feminine, WHRs feel less comfortable and self-report lower body esteem and self-efficacy than men with higher, more masculine, WHRs. ) is commonly considered attractive. To enhance their perceived attractiveness, some women may artificially alter their apparent WHR. The methods include the use of a corset to reduce the waist size and hip and buttock padding to increase the apparent size of the hips and buttocks. In an earlier attempt to quantify attractiveness, corset and girdle manufacturers of the 20th century used a calculation called hip spring (or hip-spring or hipspring), calculated by subtracting the waist measurement from the hip measurement. However this calculation fell into disuse because it is a poor indicator of attractiveness; for example, a hip spring of 250 mm would likely be considered quite attractive for an average-sized adult woman, but a child or petite woman with the same number would more likely be seen as malnourished. WHR versus BMI attractiveness is related to fertility, not fat content. A study performed by Holliday used computer generated female body shapes to construct images which covary with real female body mass (indexed with BMI) and not with body shape (indexed with WHR), and vice versa. Twelve observers (6 male and 6 female) rated these images for attractiveness during an fMRI study. The attractiveness ratings were correlated with changes in BMI and not WHR. The results demonstrated that in addition to activation in higher visual areas, changes to BMI had a direct impact on activity within the brain's reward system. This shows that BMI, not WHR, modulates reward mechanisms in the brain and that this may have important implications for judgements of ideal body size in eating-disordered individuals. Another study, conducted by Adrian Furnham, was used as an extension of Singh and Young's 1995 investigation. A total of 137 participants were in the study. There were 98 female participants. The age range was between 16 and 67. The majority of participants were undergraduates, and 90% were white British, the remainder being Asian (East Indian) and African. Their educational and socio-economic backgrounds (nearly all middle class) were fairly homogenous, and none had previously participated in any studies involving female body shape or attractiveness. It was predicted that the effect of breast size on judgment of attractiveness and age estimation would be dependent on overall body fat and the size of the waist-to-hip ratio. All the participants were given a booklet with eight pictures in total. Each figure was identified as heavy or slender, feminine WHR or masculine WHR, and large-breasted or small-breasted. The participants rated the figures for four personal attributes (attractiveness, healthiness, femininity, and kindness/understanding). The study authors concluded "Hence, it can be predicted that the preference for a low WHR results from male preference for women at peak residual reproductive value, just prior to first probably fertile ovulatory cycle (and with no previous children). ==Food==

A number of studies have been carried out with focus on food composition of diets in relation to changes in waist circumference adjusted for body mass index. Whole-grain, ready-to-eat, oat cereal diets reduce low-density lipoprotein cholesterol and waist circumference in overweight or obese adults more than low-fibre control food diets. Weight loss did not vary between groups. In an American sample of 459 healthy men and women participating in the ongoing 'Baltimore Longitudinal Study of Aging', the mean annual increase [with age] in waist circumference was more than 3 times as great for the participants in the white-bread cluster compared with the participants using a diet that is high in fruit, vegetables, reduced-fat dairy and whole grains and is low in red or processed meat, fast food and soft drink. A 2011 study suggests that a dietary pattern high in fruit and dairy and low in white bread, processed meat, margarine, and soft drinks may help to prevent abdominal fat accumulation. == See also ==