Gynoid fat distribution

Gynoid fat is mainly composed of long-chain polyunsaturated fatty acids.[2] It is proposed that babies which are breast-fed are more likely to have increased cognitive capabilities due to these fatty acids being present in the breast milk, as they have been suggested to aid early brain development in foetuses and newborns.[4] The most notable fatty acids found in human breast milk are Docosahexaenoic acid and Arachidonic acid, which have been shown to play crucial roles in the healthy formation and functions of neurons.[5]

Gynoid fat contributes toward the Female body shape that girls begin to develop at puberty; it is stored in the breasts and the hips, thighs and bottom.[6] This process is modulated by estrogen, the female sex hormone, causing the female form to store higher levels of fat than the male form, which is affected primarily by Testosterone.[7]

See Android fat distribution

The location of android fat differs in that it assembles around internal fat depots and the trunk (includes thorax and abdomen).[2] Android fat has more of a survival role and is utilised by the body as an energy source when energy supplies are low, in contrast to the reproductive functions of gynoid fat.[8]

The differences in gynoid fat between men and women can be seen in the typical "hourglass" figure of a woman, compared to the inverted triangle which is typical of the male figure. Women commonly have a higher body fat percentage than men and the deposition of fat in particular areas is thought to be controlled by sex hormones and GH.[13]

The hormone estrogen inhibits fat placement in the abdominal region of the body, and stimulates fat placement in the gluteofemoral areas (the buttocks and hips). Certain hormonal imbalances can affect the fat distributions of both men and women. Women suffering from polycystic ovary syndrome, characterised by low estrogen, display more male type fat distributions such as a higher waist-to-hip ratio. Conversely, men who are treated with estrogen to offset testosterone related diseases such as prostate cancer may find a reduction in their waist-to-hip ratio.[14]

Sexual dimorphism in distribution of gynoid fat was thought to emerge around puberty but has now been found to exist earlier than this.[15]

Gynoid fat bodily distribution is measured as the waist-to-hip ratio (WHR), whereby if a woman has a lower waist-to-hip ratio it is seen as more favourable.[16] Studies have found correlations between WHR and Intelligence quotient (IQ) levels. It was found not only that women with a lower WHR (which signals higher levels of gynoid fat) had higher levels of IQ, but also that low WHR in mothers was correlated with higher IQ levels in their children.[17]

Android fat distribution is also related to WHR, but is the opposite to gynoid fat. Instead, android fat is deposited in the waist, breasts, buttocks and thighs, but can give an unattractive appearance, as it gives women a ‘T-shaped” body and is more lumpy.[18] The ratio of a woman’s gynoid to android fat is used to measure her WHR, whereby the lower the WHR, the higher gynoid to android fat ratio, which is perceived as more attractive for women. As women with higher levels of gynoid fat distribution are seen as more attractive, this enables them to access highly desirable male mates.[19] WHR is related to various markers of health and fertility, for example a high WHR is correlated with: a low estrogen/testosterone ratio (this means that a woman has more of a 'T-shaped' body which is seen as less healthy and attractive); a high ratio is also correlated to circulatory system problems such as heart attacks and strokes; more disease (e.g. cancer); and is a general sign of increased age and hence lower fertility, therefore supporting the adaptive significance of an attractive WHR.[20] This advantage of being more fertile has been supported by various studies, for example artificial insemination studies involving sperm donors, where the best predictor of success is a low WHR.[21] Similarly, a high WHR has been associated with impairment in the pregnancy rate of IVF (in vitro fertilisation) embryo transfer women due to the higher levels of android fat distribution.[22] Further studies have also found that oestrogen replacement in women lowers the WHR in pre- and post-menopausal women, and that this is because oestrogen replacement maintains gynoid fat distribution in the body.[23]

Both android and gynoid fat are found in female breast tissue.[24] Females develop breasts around puberty and breasts with less android fat and more gynoid fat are firmer. Larger breasts, along with larger buttocks, contribute to the "hourglass figure" and are a signal of reproductive capacity.[25] The proportion of gynoid fat is a good predictor of female reproductive capability, such as conception probability and likelihood of successful pregnancy.[26] As humans evolved and became bipedal, other ways of signalling such as sexual swelling became less visible and consequently other forms of sexual signalling had to develop.[27] Being able to store an optimum amount of gynoid fat requires a female to have access to resources such as food and therefore is an honest signal of having sufficient energy resources to successfully reproduce.[27]

However, not all women have the most optimal distribution of gynoid fat, hence there are now trends of cosmetic surgery, such as liposuction or breast enhancement procedures which give the illusion of attractive gynoid fat, and can create a lower waist-to-hip ratio (WHR) or larger breasts than some are able to achieve naturally.[28] Other examples include micrograft surgery,[29] which involves the deposition of adipose tissue, previously taken from the waist, into the buttocks. This achieves again, the lowered WHR and the 'pear-shaped' or 'hourglass' feminine form; all deemed attractive features.[30] Cosmetic surgery represents a vast body of evidence supporting the hypothesis that people are evolutionarily programmed to be attracted to health features.

A biological ornament is sexual signal of attractiveness involved in the process of sexual selection, and functions as an honest signal of quality.[31] Sexual ornamentation of females involves more attractive levels of gynoid fat, meaning bigger breasts and buttocks and a low WHR these all signal health, fertility, genetic quality, and thus attractiveness.

Ornamentation is important in female intrasexual competition, which involves female-female competition for potential mates and their associated resources. Since the function of such ornamentation is to compete for male resources, females with a lower WHR are favoured.[32] Ornamentation also plays a key role in male mate choice, where again, females with a low WHR are favoured as they are more attractive.[30] The benefits of attractive ornamentation are gaining resources from males. Attractive ornamentation allows more access to highly desirable males with material resources (e.g. food) and higher mating success. Further benefits of attractive ornamentation are seen in the protection of a female and her offspring. This can be from sexually coercive males, or from raiding males who are looking to capture females.[33]

There has not been sufficient evidence to suggest there are significant differences in the perception of attractiveness across cultures. Females considered the most attractive are all within the normal weight range with a low waist-to-hip ratio (WHR), regardless of fluctuations in BMI, and this finding can be seen as consistent across Indonesian, Chinese, White and African-American young men and women.[29][34] Psychologists have argued that evolutionary selection processes have facilitated this relationship between WHR and female attractiveness, which has resulted in a consensus that seems to transcend cultural boundaries.[35]