Obesity can cause decreased sexual function, male infertility, and female menstrual and fertility problems.

53. Does obesity cause decreased sexual function?

Mild obesity usually does not affect sexual function.

Moderate to severe obesity can lead to varying degrees of sexual dysfunction.

Obese individuals, due to excess body fat, experience an excessive accumulation of sex hormones in their adipose tissue.

Scientific research has found that obese men have lower levels of free and bound testosterone in their plasma than men of normal weight, and there is a trend that the heavier the body weight, the lower the level of male hormones.

In severely obese men, androgen levels are reduced while estrogen levels are increased. Androgen levels can be reduced by one-third compared to normal men, while estrogen levels can be increased by one to two times.

Androgens play a role in stimulating male secondary sexual characteristics, maintaining normal libido, and fertility.

A decrease in male hormone levels can lead to decreased libido in men, resulting in disharmony in their sex life and even erectile dysfunction.

The main changes in sex hormones in obese women are: (1) a relative increase in androgens, which can be up to twice that of people with normal weight. (2) an increase in estrogen and an imbalance in the ratio of estrogen to estradiol, with the estrogen/estradiol ratio being twice that of normal people. (3) persistently high estrogen levels inhibit the pituitary gland from secreting follicle-stimulating hormone and luteinizing hormone, which can cause menstrual disorders and infertility.

Because lipid metabolism affects sex hormone levels, obese girls may experience earlier menarche, while obese boys may have smoother facial skin and less body hair.

Recent clinical findings have also revealed that severely obese adolescents may have underdeveloped testes or lack of secondary sexual characteristics, and may also exhibit female-like physical changes, such as excessive fat in the chest and abdomen, fat accumulation in the chest resembling female breast development (without breast tissue), and rounded buttocks, which can often cause psychological burden for young men.

The above symptoms are mostly secondary obesity, and therefore are often accompanied by endocrine abnormalities, ovarian insufficiency, Cushing's syndrome, polycystic ovary syndrome, as well as central obesity with incomplete development of sex organs, obesity-related infertility syndrome, etc.

Why does obesity cause male infertility?

Modern medical research shows that male infertility in obese men is mainly due to two factors: firstly, obesity can lead to varying degrees of sexual dysfunction.

Because adipose tissue has the ability to convert the aromatic ring of androgens into estrogens, in men, especially those with severe obesity, androgens are reduced and estrogens are increased.

An imbalance in the ratio of estrogen to androgen can cause obese men to experience low sexual function, with impotence and decreased libido being the most common symptoms.

On the other hand, obese individuals accumulate excessive fat in their scrotum due to the large amount of fat stored in their bodies.

In obese men, the scrotum is filled with a lot of fat, which will have many effects on male fertility: (1) Insulation: Fat has a heat-preserving effect and will prevent the scrotum from dissipating heat normally. The testes need a "low temperature" environment that is 1.5 to 2°C lower than the body temperature, otherwise it will affect sperm secretion. (2) Compression: On the one hand, excessive fat can squeeze the testes toward the abdomen, making the local temperature of the testes too high.

On the other hand, excessive fat in the scrotum can compress the spermatic cord vessels. If the artery is compressed, the testicle will be ischemic; if the vein is compressed, the testicle will become congested.

These are detrimental to spermatogenesis. (3) Weakening the strength of the cremaster muscle. There is a cremaster muscle in the scrotum. When this muscle contracts, the testicle can move up and down, which can help the blood in the spermatic vein return.

Excessive fat in the scrotum can hinder the normal activity of the cremaster muscle, and over time, the cremaster muscle will gradually atrophy and become thinner.

The combined effect of these two factors leads to male infertility in obese men.

This type of male infertility can be treated by losing weight or surgically removing excess fat from the scrotum, which can restore male fertility to normal.

Does obesity in women affect menstruation and fertility?

We see many obese women in our lives.

According to relevant statistics, the proportion of obese women is significantly higher than that of obese men.

This is because women's rates of weight gain vary depending on their specific stage of life. For example, the rate of weight gain is as high as 40.9% during postpartum and 35.7% during the premenopausal period. In contrast, the probability of weight gain during puberty and menopause is generally below 10%.

Statistics show that in a study of 100 women with menstrual disorders, some experienced amenorrhea, some had oligomenorrhea, and some had dysfunctional uterine bleeding.

Of these 100 people, 43 were overweight by more than 20%.

They also conducted a long-term observation of 32 women who had amenorrhea due to obesity. All of them underwent weight loss therapy. As a result, 13 out of the 15 women who successfully lost weight had their menstrual cycles return to normal, while none of the 17 women who failed to lose weight had their menstrual cycles return to normal.

The examples above show that obesity is indeed related to menstrual disorders. Although the exact relationship is not yet fully clear, it is clear in at least a few aspects.

First, obese women have higher blood estrogen concentrations than women of normal weight. The excess estrogen comes from several sources: First, human fat cells act as a processing plant for estrogen, converting androgens into estrogens (the ovaries and adrenal cortex can also synthesize small amounts of androgens).

Obese people have more fat cells and higher estrogen secretion.

Second, in women of normal weight, estrone (an estrogen-like substance) is metabolized into inactive α-hydroxyestrone, but in obese women, estrone is metabolized into estriol, which still has a weak estrogenic effect.

Third, it is known that most estrogen and androgen (specifically testosterone) in the blood are bound to a protein called sex hormone-binding globulin. Sex hormones bound to this protein cannot exert their physiological effects. Only a small portion of sex hormones that are not bound to the protein, called free sex hormones, are the ones that truly exert their effects.

Obese women have lower levels of sex hormone-binding globulin than women of normal weight, thus increasing the levels of free estrogen and free testosterone that can exert their effects.

High levels of estrogen in the blood caused by various factors can hinder ovulation, leading to infertility, menstrual disorders, and in severe cases, endometrial hyperplasia (i.e., dysfunctional uterine bleeding) and even endometrial cancer. This is one of the reasons why the incidence of endometrial cancer is higher among obese women.