Men tend to grow belly in middle age, which may be related to this

Author: Xiao Hengjun, Chief Physician, The Third Affiliated Hospital of Sun Yat-sen University

Reviewer: Wang Tao, Chief Physician, Tongji Hospital Affiliated to Tongji Medical College of Huazhong University of Science and Technology

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"Big belly" is a problem that troubles many middle-aged men. Why do men gain weight so easily in middle age? In general, we think that this is related to stressful life, irregular diet, poor sleep and lack of exercise, but in addition to these, obesity is actually closely related to the male hormone testosterone in men.

Testosterone is the main component of androgen and the most important sex hormone in the human body. It can be produced in both men and women, but the testosterone level in men is much higher than that in women.

The main function of testosterone is to promote the appearance of male characteristics and is of great significance to the production and function of sperm.

Studies have found that testosterone has a positive effect on strengthening male muscles and protecting physical health, such as blood sugar control, prevention of cardiovascular and cerebrovascular diseases, fat distribution, anti-infection, and prevention of Alzheimer's disease [1].

1. Testosterone levels and male weight affect each other

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Generally speaking, lower testosterone levels can lead to weight gain in men, but this relationship is not constant and is related to different age stages.

During puberty, if male testosterone levels drop, some teenagers will become thin and lose weight, which is caused by insufficient muscle mass and decreased bone density. However, low testosterone levels can also easily lead to fat accumulation, so some teenagers are prone to obesity while lacking muscle mass and decreasing bone density, becoming a "weak fat man."

In middle-aged and elderly men, as they age, their testosterone levels gradually decrease. When testosterone drops to a certain level, it can also lead to an increase in adipose tissue, especially visceral fat, which further causes the body to be insensitive to leptin and leptin resistance, making leptin unable to inhibit fat synthesis and promote fat decomposition.

That is to say, a decrease in testosterone levels will lead to leptin resistance, thereby aggravating obesity. In addition, obesity will further lead to a decrease in testosterone levels, and the two are mutually influential.

How does testosterone affect male weight ?

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Testosterone mainly affects men's weight through three physiological effects: increasing bone density, promoting muscle growth and reducing body fat content.

1. Increase Bone Density

The mechanism by which androgens exert their effects on the skeletal system is still unclear, but increasing evidence suggests that testosterone plays an important role in maintaining bone density in humans.

During puberty, the testosterone level in men increases. Under the action of testosterone, men's height increases suddenly. At the same time, testosterone promotes calcium salt deposition, making the bones of adolescent men dense. At this time, men's bones will become stronger and their weight will increase. However, if the testosterone level decreases, it will lead to a decrease in bone mass, osteoporosis, and an increased probability of fractures.

2. Promotes Muscle Growth

Testosterone can also promote the growth of muscle mass, making the muscles of adolescent males more developed and their weight naturally increased. This also explains why testosterone preparations can be used as "stimulants". There have been many "stimulant" scandals in the history of world sports, and many of them were athletes who used testosterone preparations to increase muscle mass and hemoglobin concentration, thereby improving endurance.

3. Reduce body fat content

Several epidemiological studies have shown that testosterone levels are significantly negatively correlated with the degree of obesity. Studies have shown that testosterone enhances norepinephrine-stimulated lipolysis, a mechanism that may be related to an increase in the number of β-adrenergic receptors. Researchers have found that in mice with androgen receptor deficiencies, the reduced lipolysis capacity of androgen action is the main cause of increased visceral fat and late-onset obesity [2].

In short, testosterone can affect the fat production process by inhibiting the differentiation and formation of new fat cells. If testosterone is deficient, it will promote the development of fat cells and lead to weight gain.

3. Three factors that affect testosterone secretion

Finally, let’s take a look at some common reasons that can easily lead to a decrease in testosterone secretion.

The first is aging. After the age of 30, the testosterone level of men begins to decline naturally, and after the age of 40, it decreases by 1% to 2% every year. This is a normal physiological phenomenon.

The second is obesity. Obesity increases the activity of aromatase in men, an enzyme that promotes the conversion of testosterone into estrogen, thereby reducing testosterone levels. At the same time, this process inhibits the function of the hypothalamus-pituitary-gonadal axis, ultimately leading to a decrease in testosterone release [2].

Bad living habits are also a factor, such as lack of sleep, excessive stress and lack of trace elements (such as zinc and vitamin D), which will affect the production of testosterone.

Finally, there is the incorrect use of testosterone drugs. Since the Roman period, people have studied the physiological effects of testosterone. It was not until the 20th century that testosterone was extracted and used as an injection during World War II. As the research on the function of testosterone became more in-depth, the abuse of testosterone became more serious.

If the medication is not taken under the guidance of a doctor, it may not only aggravate the problem of low testosterone, but also lead to other adverse reactions, such as testicular atrophy, sperm production and dysfunction, and prostate dysfunction.

Testosterone has a wide range of physiological functions, especially for men, throughout their lives from embryonic development to aging.

If you have entered middle age, between 40 and 50 years old, and have symptoms such as fatigue, frequent daytime dozing, muscle atrophy, sleep disorders, abdominal obesity, hair loss, depression, anxiety, etc., you can go to the hospital for a comprehensive physical examination and hormone level test, seek the opinions and suggestions of professional doctors, and avoid taking hormone drugs on your own.

References

[1] Sun Tao, Feng Bing, Chen Jing. Happy Menopause: You Can Live a More Wonderful Life. Beijing: China Population Press, 2019.

[2] Tao Jun. Research progress on testosterone and hyperlipidemia, energy metabolism disorders and obesity. Journal of Microcirculation, 2022, 32(1): 76-79, 86.