Classification of obesity: simple obesity and secondary obesity

III. Find out which type of obesity you have

Although all obese people have excess body fat, the manifestations of obesity vary greatly depending on the type of obesity.

To determine the cause of obesity, one should first have a basic understanding of the different types of obesity before taking appropriate measures to address it.

(a) Simple obesity

Simple obesity refers to obesity without obvious endocrine or metabolic diseases.

In other words, simple obesity is not caused by any specific disease, but is mainly caused by excessive energy intake and reduced calorie expenditure, which leads to the excess calories being converted into fat and stored in the body. Most of the obese people we usually see belong to this type of obesity.

Simple obesity is further divided into two categories: constitutional obesity and acquired obesity.

1. Constitutional obesity: Constitutional obesity is a type of obesity that begins in infancy. Patients with this type of obesity often have a good appetite and excessive nutrition from around six months after birth. Their anabolism exceeds their catabolism, leading to the proliferation of fat cells.

Recent studies have found that fat cells have a highly active period of proliferation from the 30th week of fetal development to one year after birth, known as the "sensitive period." Excessive nutrition during this period can lead to fat cell proliferation.

This type of obesity often has a family genetic predisposition, and dietary control measures are not very effective. However, if this type of obesity can be prevented and treated early, these sensitive individuals will be less likely to become obese.

However, if left to develop naturally, it will become uncontrollable.

2. Acquired obesity: Acquired obesity, also known as nutritional obesity, is often caused by overeating due to patients' intentional or unintentional overeating.

Patients typically have a strong craving for sweets, such as sugars and pastries.

Some patients have a particular fondness for greasy foods, such as fatty meat and fried foods.

Patients often develop obesity after adulthood (after age 20) due to overnutrition, hence it is also known as adult-onset obesity.

Acquired obesity involves only enlarged fat cells without an increase in the number of cells.

Its fat is mainly distributed in the trunk, and treatments such as diet control are easily effective.

(II) Secondary obesity

Secondary obesity is symptomatic obesity caused by a certain disease as the primary cause, and this type of obesity accounts for less than 5% of obese patients.

At this time, obesity is only one of the manifestations of the primary disease, not the main manifestation, let alone the only manifestation.

For this type of obesity, the underlying disease should be treated; otherwise, it will be impossible to achieve the goal of weight loss.

Secondary obesity can be further divided into endocrine disorder obesity and congenital abnormal obesity, depending on the cause of obesity.

1. Endocrine disorder-related obesity

(1) Hypothalamic obesity: The hypothalamus is an important central nervous system for human life activities. Its main physiological function is to regulate energy balance and nutrient intake.

In this area, there is a center that specifically controls the feeling of being full, called the satiety center; and there is another center that specifically controls hunger, called the feeding center.

If, due to certain reasons such as trauma, inflammation, or tumors, the hypothalamus becomes dysfunctional, causing an imbalance between the satiety center and the feeding center, the person will not feel full when they should, and will inevitably eat endlessly, thus overeating.

It's easy to understand why excessive calorie intake leads to obesity.

Most patients with hypothalamic obesity develop obesity rapidly within a short period of time, with particularly noticeable obesity in the breasts, lower abdomen, and areas near the external genitalia.

The face and limbs are relatively thin, and the fingers (toes) are thin and pointed.

Delayed sexual development or sexual dysfunction; small testes in boys that often have not descended; unusually large breasts in girls with atrophied mammary glands; and infantile vulva.

In adults, the disease often presents with loss of sexual function, lack of sperm, amenorrhea, and infertility.

Hypothalamic obesity patients are prone to drowsiness or insomnia, excessive sweating or anhidrosis, high or low body temperature, urinary and fecal incontinence, mental abnormalities, unpredictable crying and laughing, and intellectual disability.

(2) Cushing syndrome: Cushing syndrome is the most important and most common disease leading to abnormal obesity. It is mostly caused by tumors in the pituitary gland leading to excessive secretion of adrenocorticotropic hormone, resulting in bilateral adrenal hyperplasia and increased cortisol secretion. It is also known as Cushing syndrome because it was first reported by the American physician Cushing.

This disease often presents with the following clinical manifestations.

①Central obesity: The patient is obese in the trunk but not in the limbs.

The face is round, like the full moon, hence the name "full moon face".

The patient's fat is distributed subcutaneously in the chest, abdomen, and back, with a prominent thick layer of fat on the neck and back, known as "buffalo hump".

② Sanguine symptoms: The patient's skin is very thin and the blood vessel walls are thin, so the face is rosy, which is called "sanguine".

③ Purple stripes: Typical purple stripes are wide in the middle and thin at both ends, with a purplish-red color. They are commonly seen on the lower abdomen, buttocks, outer thighs, armpits, and breasts.

④ Excessive hair growth: This is especially prominent in female patients, with thicker and more abundant hair on the face, as well as increased armpit and pubic hair.

⑤ Some patients have elevated fasting blood glucose, positive urine glucose, hypertension, osteoporosis, susceptibility to infection, sexual dysfunction, and nervous system dysfunction.

(3) Hypothyroidism-related obesity: The thyroid gland is the largest endocrine gland in the human body, and its main physiological function is to regulate the body's heat metabolism.

When thyroid function is low, energy metabolism decreases and energy consumption is reduced, resulting in weight gain, apathy, dullness, and the formation of a typical myxedema facies.

Because hypothyroidism and weight gain can cause a bulky appearance, it is easily confused with obesity.

However, hypothyroidism is often accompanied by symptoms in other systems, such as cold intolerance, reduced sweating, fatigue, drowsiness, lethargy, slow movements, decreased appetite, dry skin, anemia, and low blood sugar.

(4) Pancreatic obesity: Commonly seen in the early stages of mild type I diabetes, pancreatic β-cell tumors. Because the body secretes a large amount of insulin, patients often experience hypoglycemia.

Hypoglycemia prompts patients to eat sweets, which quickly leads to obesity.

Because the characteristic of this disease is fasting hypoglycemia, the symptoms disappear rapidly after sugar is given. Therefore, patients often experience palpitations, hunger, sweating, tremors in the hands and feet, and even convulsions when fasting, which improve immediately after sugar is given.

2. Congenital dysplastic obesity: Congenital dysplastic obesity is mostly caused by genetic and chromosomal abnormalities and is commonly seen in the following diseases.

(1) Congenital ovarian hypoplasia: These women have primary amenorrhea, immature reproductive organs, short stature, intellectual disability, webbed neck, cubitus valgus, and short fourth metacarpal bone.

(2) Congenital testicular hypoplasia: These males are generally tall, with long limbs, finger span greater than body length, pubic symphysis distance greater than 1/2 of height, incomplete development of secondary sexual characteristics, infantile genitalia, and feminized breasts.

(3) Glycogen storage disease: This disease is a congenital recessive metabolic disease caused by a lack of glucose phosphatase in cells such as the liver and kidneys, which leads to an obstruction in the breakdown of glycogen, resulting in the accumulation of glycogen in various tissues and enlargement of the liver and kidneys.

There are usually no obvious symptoms in infancy, but the symptoms become more obvious as the child grows older.

The patient has developmental delays, is short in stature (dwarf-like), obese, has a full face, especially in the lower abdomen.

3. Inner table cranial hyperplasia: almost all of them are women, and it is more common after menopause. They have headaches, which are often quite severe. About half of the patients are obese, and the headaches are mainly in the trunk and proximal extremities.

Skull X-rays are diagnostically significant.

(III) Investigate the cause of obesity

With so many types of obesity, which type do you belong to? You can look for the reasons from the following aspects.

1. Based on the occurrence of obesity: If a person has been obese since childhood and there are tall or obese family members, eats a lot, and the obese person's weight is relatively uniform, this situation is mostly constitutional obesity.

Slow weight gain in adulthood, accompanied by overeating and reduced exercise, and with no other physical discomfort besides obesity symptoms, is often a sign of acquired obesity.

If an adult experiences acute weight gain, they should recall their medication history, physical health status, such as a history of head trauma, encephalitis, stroke, etc., and whether it occurred during the recovery period of an illness, after major surgery, or after childbirth.

2. Based on the physical examination: pay attention to height, weight, muscle development, and whether there is edema or congenital malformation.

Pay attention to body shape. Generally, women's fat is mostly distributed in the lower body, mainly in the hips and lower limbs; men's fat is mostly distributed in the upper body, mainly in the chest and abdomen. If a woman is masculine or a man is feminine, attention should be paid to the development of secondary sexual characteristics.

Furthermore, the waist-to-hip ratio can be used to determine whether someone has central obesity.

In symmetrical obesity, the thickest part is the buttocks, meaning the hip circumference is the largest; in central obesity, the thickest part is the abdomen, with the waist circumference being the largest. In this case, the possibility of increased cortisol should be considered.

Some postmenopausal women experience a gradual decrease in hip circumference and an increase in waist circumference over the years. Their limbs become thinner and their torso thickens. At this time, they may also experience central obesity with a waist circumference greater than their hip circumference, but they do not have characteristics such as a moon face or buffalo hump. The possibility of increased cortisol is not high.

Note any neurological or mental disorders, and any developmental abnormalities of the reproductive organs.

3. Auxiliary examinations and endocrine function tests: For some patients who may have secondary obesity, further necessary auxiliary examinations and endocrine function tests should be performed.

Auxiliary examinations include X-ray examination, CT and MRI examination, B-ultrasound and radionuclide examination, chromosome examination, etc.

Endocrine tests can include indicators that reflect thyroid function, such as T1 and T₄; indicators that reflect pituitary and adrenal function, such as urinary 17-hydroxyl, 17-keto, and urinary free cortisol; indicators that reflect sexual function, such as serum testosterone and estradiol; and indicators that reflect pancreatic function, such as fasting blood glucose, serum insulin, and glycosylated hemoglobin.

The choice of which tests to undergo should be determined by a doctor to ascertain the type of obesity you have.