Abstract
The hunger and sex hormones like
many other hormones in human body work in coordinated way to complete the
assigned physiological task. Some of the primary functions they do
independently e.g. Leptin plays a crucial role in regulating energy balance and
appetite but it directly or indirectly coordinates with estrogen to participate
in reproductive functions. Experimental studies provided enough evidence
unequivocally that the circulating estrogen may be responsible for the elevated
levels of leptin in blood circulation. In addition to this coordination,
estrogen is also capable of stimulating in the leptin levels in the serum which
peak at mid-cycle synchronising with luteinizing hormone pulses. Gonadotropins
and growth factors are responsible for promoting ovarian granulosa and theca cells
functions and oocyte maturation if the normal range of serum leptin levels is
maintained. Estradiol, primarily inhibits appetite and promotes satiety,
leading to reduced food intake though in some cases, like after fasting or low
blood sugar, it may actually promote re-feeding. This is thought to be due
to the way estradiol influences meal size and onset of satiety. Based on the
nutritional status, estradiol, a potent form of estrogen, induces bidirectional
actions on feeding.
Keywords: Gonadotropins,
Oocyte maturation, Satiety, Human behaviour
1. Introduction
Hormones are signalling
molecules produced by endocrine glands placed at different sites in
the body. These hormones have a pivot role in regulating physiological
processes as well as behavioural activities in humans such as digestion,
metabolism, respiration, sensory perception, sleep, excretion, lactation,
stress induction, growth and development, movement, reproduction and mood
manipulations, in other words most of the important physiological functions.
They exhibit a significant role to play everything from sleep and stress
to food cravings and weight loss1-3.
Hunger and sex are also controlled by co-ordination of different sets of
hormones4,5.
Leptin, a hormone primarily
produced by adipocytes that plays a crucial role in regulating energy balance
and appetite6. Leptin is a signalling
molecule to communicate between fat stores of the body and the brain there by
influencing hunger, metabolism and other physiological processes. Leptin
also impacts neuroendocrine function, immune responses and other metabolic
processes7-9. A number of
endocrine glands release hormones when stimulated by hormones released by other
endocrine glands. There is a relationship between leptin and estrogen10, though they are produced in the two
different organs performing entirely different functions and belonging to
different body systems.
Leptin also affects ovarian
function, since studies suggest that it may directly influence granulosa cells
to reduce estradiol production indirectly playing a role in reproductive health.
Estrogen can interact with other hormones that influence appetite, such as
leptin and ghrelin, which regulate hunger and satiety. For instance,
estrogen can help regulate leptin levels, which signal satiety11. The developing ovarian follicles (granulosa
cells) contributes to an increase in estrogen levels during follicular phase in
turn there is an increase in circulating leptin.
Evidence from studies provides a
clue that leptin can also directly influence the ovarian function, potentially
by acting on granulosa cells to regulate estradiol production as well in
addition to its influence on the development and maturation of ovarian
follicles. This conclusion is possible because higher leptin levels have been
observed during controlled ovarian hyperstimulation. The role of estrogen in
elevating the circulating leptin concentration in humans and rats12,13 as well as the reduction in leptin
expression in ovariectomized rats can be reversed by estrogen administration confirms
the relationship between leptin and estrogen14-16.
Estradiol, a form of estrogen,
though inhibits and promotes satiety, its effects depend on the
nutritional status of the host17,18. Estradiol
also promotes bidirectional actions on feeding primarily inhibits appetite and
promotes satiety, leading to reduced food intake, but in some cases, like after
fasting or low blood sugar, it may actually promote re-feeding. This is
thought to be due to the way estradiol influences meal size and onset of
satiety. Santollo J, et al, suggested that that estradiol (E2) inhibit food
intake through estrogen receptor alpha (ERα) transcriptional activity (t-a) via
hypothalamus19.
During mid cycle estrogen
stimulates an increase in the titre of serum leptin, thereby synchronizing with
nocturnal luteinizing hormone pulses. Serum leptin levels (normal range (10-20
ng/mL) promote ovarian granulosa and theca cell functions and oocyte maturation
in combination with gonadotropins and growth factors17.
Estrogen, though a sex hormone is
also capable of regulating appetite and food intake because it can suppress
food intake and meal size; influencing the body processes of generating energy
from food20. The other sex
hormones like progesterone and testosterone also have an influence on the
hunger regulation other than reproductive function. The mechanism of regulating
hunger by estrogen is a complex mechanism, including actions on the estrogen
receptors in the brain particularly in the amygdala and its impact on energy
expenditure, which is involved in hunger-enhanced memory for food stimuli.
Estrogen can also influence how the body uses energy, by inducing ketabolism as
well as the distribution of body fat21.
New research indicates that
neuroestrogens help suppress appetite since in aromatase knocked out mice that
cannot synthesize estrogens in a systemic manner. As a result, in these mice
increased food intake and body weight compared with their aromatase-expressing counterparts.
When aromatase expression was restored the action of neuroestrogens influencing
appetite was observed22.
1.1. Evolution
of sex and hunger
Sex and hunger are two
distinct physiological functions yet interconnected. While hunger is a
fundamental drive for survival, sexual motivation is primarily meant for
reproduction and the continuance of species. Evolutionary pressures have
shaped both hunger and reproduction23,24,
with sex often influencing behaviour in ways that may not directly maximize
individual survival, but enhance the reproductive success of the species. Here
are some points to be considered a more detailed look:
1.1.1. Evolution
of hunger:
1.1.2.
Evolution of sex:
· Reproduction:
in biological sense sex is fundamentally about the mixing of genetic material
to produce offspring with new combinations of genes. In other words, propagation
of species, but variation because of combinations. This increases genetic
diversity, which can be beneficial in adapting to changing environments27.
·
Beyond reproduction: Beyond
reproduction, sex can also have a vital involvement in social bonding, mate
selection and even the development of complex social structures it’s a
fact that sex plays an important role in human relationships, emotional
well-being and overall health. It facilitates intimacy, strengthens bonds
and can provide pleasure, relaxation and a sense of connection. Sex can
also have a positive impact on physical health, including lowering blood
pressure and improving sleep27,28.
·
Sexual selection:
Evolutionary pressure exerted on individuals is responsible to select traits
that enhance the ability to find a mate, as well as directly benefit survival
value in sexual selection. This can lead to the development of elaborate
displays or competitions. Sexual selection is a mechanism operated in
nature where members of one sex choose mates of the other sex to mate with
(intersexual selection), resulting in completion among the members of the same
sex to get the mate of the opposite sex (intrasexual selection).
1.1.3. The interconnection:
· Resource Availability: In some
species, resource availability can influence the timing and frequency of sexual
activity predominantly because, individuals normally reproduce when enough
resource are at their disposal for the young once especially. Intersexual activity in
many species is observed to get reduced due to resource scarcity29.
·
Human Behaviour: In humans, the
relationship between hunger and sex is complex. Both hunger and sexual drive
are fundamental human motivations, but they are also linked in various ways,
including through brain regions, hormones and even behavioural
changes. Hunger, as a physiological drive, can impact sexual behaviour,
potentially reducing libido when energy stores are low. Conversely, sex
can have appetite-suppressing effects due to the release of hormones like
oxytocin. Emotional factors come in to such situation linking
psychological well-being30.
·
While some studies suggest a
correlation between high hunger and increased libido, particularly in males,
other research indicates that severe calorie restriction can suppress sexual
desire.
1.2.
Sex vs. food
Scientific data suggests that
during resource scarcity such as food couples show eagerness to socializing
with members of the opposite sex. Depending on situation hunger proves to
increase sexual desire. There is a complex interplay between hunger, appetite,
socialization and sex drive. However, so far it is not well defined whether higher
libido can result due to hunger or appetite suppression. Leptin receptor
neurons when activated in mice, social interaction was given priority despite
hunger or thirst. Liu Z, et al, suggested from the preliminary study that
overeating or rebound eating after calorie-restricted dieting is a better
practice31.
1.3.
Leptin influences libido
Neuroscientists observed that both
types of neurons one which carry receptors for leptin and the other which
produce neurotensin, are involved in hunger and thirst in addition in sexual
behaviour32. On activating the
neurons with leptin receptors, Martin, et al, observed changed behaviour in the
mice in all the three experimental conditions such as well-fed, hungry after
fasting overnight and chronically hungry (after spending five days on a
restricted diet)33; and were surprised
in activating the leptin neuron did nothing in mice from well fed and fasting.
Animals those who had plenty to eat displayed, a priority to find sexual
partners, as usual, but the starved mice were indifferent to sex and went for
search for food first.
1.3.1. Sex and
hunger relationship:
The
following conclusions were drawn in the laboratory experiments with mice
·
In the mice who had plenty to eat
and drink activating the leptin neuron did nothing., as well as in,
·
Chronically hungry mice also
behaved as mice who had plenty to eat and drink.
·
The well-fed mice prioritized finding
sexual partners,
·
The very hungry mice said no to sex
and went for the food.
·
Moderately hungry mice shifted
their priorities from eating and drinking to sexual desire under the
influence of activated the leptin neurons, but in the same group on, activating
the leptin neuron shifted their priorities from eating and drinking
to sexual desire. They were able to ignore minor hunger or thirst in order
to find a sexual partner and have sex.
1.4. Hunger
increases sexual desire
Scientific studies established that
there is a complex interplay between hunger, appetite, socialization and sex
drive. However, the link between hunger and elevated libido is yet to be
established. The study also provides a clue that hunger curbs libido but minor hunger
easier to ignore when sex becomes priority34.
Leptin is not capable of inducing libido. But calorie restriction can improve
sex drive, unlike negative impact on sex drive during extreme calorie restriction9. This must be the reason for not able to
reduce food intake for a longer period though dieting is possible for a short
duration35.
1.5.
Obesity linked low sex drive
Obesity has a negative impact on
libido and sexual desire. Link between body mass index (BMI) with physical
limits on sexual activity and reduced sexual life score, sexual desire,
frequency of sexual activity and satisfaction with sex has been established.
Obesity has a profound role to play
in sexual dysfunction, though weight loss through medication or surgery may
help restore sexual function. Scientific research is wanting to have a better
understanding36. Excessive leptin
production in response to overeating or in states of leptin resistance
lead to decreased reproductive function in obese men36,37.
1.6.
Improve libido by manipulating hunger
Libido is influences by many
factors such as body image and self-esteem and so sexual arousal is easy to
manipulate. Regulating hunger and maintaining a moderate bodyweight can
indirectly improve libido. A healthy, balanced diet, rich in lean proteins
and vegetables, can help prevent disorders that affect sex drive, while also
boosting overall energy levels. Additionally, a stable body weight can
positively impact both physical and psychological factors related to libido.
Diet and hunger regulation can
impact libido directly by
· Hormonal balance:
A balanced diet rich in nutrients like zinc, found in foods like oysters and
pumpkin seeds, can help boost testosterone levels, which are important for
sexual function in both sex.
Blood flow:
Foods like watermelon, which contain citrulline, can help improve blood flow,
which is crucial for sexual arousal and performance.
Energy levels:
A healthy diet provides the energy needed for sexual activity and overall
well-being.
Stress reduction:
A balanced diet can help reduce stress, which is known factor in low
libido.
Weight management:
Maintaining a moderate weight can improve physical and psychological factors
related to libido.
Gaining Sex Drive by losing weight
is possible since obesity is the one of the causes of low sex drive and with
the best nutrition both issues can be solved.
The proper selection of nutrient may
help to solve both the problem of sex life and weight control.
· Pomegranate:
Pomegranate helps in improving sex life, by regulating blood flow.
Vitamin D:
vitamin D helps in strengthening immunity and enhance calcium uptake for strong
bones, it also supports testosterone levels which plays a crucial role in male
sexual function. Men who suffer with sexual performance also suffer with a
vitamin D deficiency.
· Lemon verbena:
Polyphenols rich lemon verbena promotes weight loss without the unwanted side
effects of medication.
· Whole grain rye:
Weight loss is more pronounced when whole-grain rye is consumed rather than
refined wheat bread. Rye bread is rich in magnesium, to maintain healthy blood
pressure. healthy blood flow helps during sex, as well as overall heart health.
Probiotics:
To maintain overall good health keeping gut microbiome healthy by supplementing
probiotics. Reduced sugar intake is good since
sugar creates havoc in our gut.
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