Diagnosis and BMI Classification
For a standardized assessment of body weight, the Quetelet index (BMI) is traditionally used. It is calculated using the formula: body weight ($kg$) / height ($m^2$). The resulting values are interpreted as follows:
- Normal: 20 to 25 $kg/m^2$.
- Overweight (initial form of obesity): 25 to 30 $kg/m^2$.
- Obesity: over 30 $kg/m^2$.
Although BMI serves as a reliable marker of risk factors, waist circumference (WC) measurement is the key method for accurately assessing fat distribution. Criteria for abdominal obesity are $\ge$ 94 cm for men and $\ge$ 80 cm for women. It is important to note that the waist-to-hip ratio is no longer used in modern medical practice. Furthermore, the abdominal fat distribution pattern can be detected even when the BMI remains within the normal range.
Abdominal Obesity and Adipose Tissue Pathophysiology
Abdominal obesity is recognized as the most prognostically unfavorable form, as it is strongly associated with malignant tumors and cardiovascular events.
The key issue lies in the properties of the adipose tissue in this specific location. Abdominal fat is dominated by brown adipocytes, which are characterized by high secretory activity. They actively produce various mediators, including leptin, interleukin-6, and tumor necrosis factor-alpha. This endocrine activity triggers a cascade of negative consequences:
- Pathological remodeling of target tissues (primarily the myocardium, blood vessels, and kidneys).
- Development of pronounced insulin resistance.
- Onset of dyslipoproteinemia and hyperuricemia.
In modern medicine, the integral assessment of a patient's condition has shifted toward comparing visceral fat with the metabolic context. The combination of obesity with disorders of lipid, purine (gout), and carbohydrate metabolism (type 2 diabetes mellitus) constitutes the primary cause of atherosclerosis and coronary artery disease.
Systemic Pathological Consequences
Obesity has a devastating impact on virtually all organ systems. The following groups of complications are distinguished:
- Cardiovascular system and hemostasis: Arterial hypertension, heart failure, and atherosclerosis develop with subsequent complications (coronary artery disease, ischemic stroke, lower extremity artery disease). In the blood coagulation system, there is an increased tendency toward thrombosis and a risk of thromboembolism.
- Respiratory system: Vascular disorders of the pulmonary circulation (pulmonary hypertension) are observed, as well as disorders of respiratory regulation—obstructive sleep apnea syndrome (OSAS) and ventilation disorders (hyperventilation).
- A specific respiratory disorder — Pickwickian syndrome: Manifests as severe daytime sleepiness against the background of marked obesity. The pathogenesis begins with alveolar hypoventilation, which leads to nocturnal apnea and cardiac arrhythmias, creating a risk of sudden cardiac death.
- Digestive and reproductive systems: Steatosis (fatty infiltration) develops in the liver, and cholelithiasis in the biliary tract. General reproductive function disorders also develop.
- Musculoskeletal system: Due to excessive load, osteoarthritis occurs, accompanied by degenerative-dystrophic changes in the joints.
- Oncology: The likelihood of developing colon, breast, prostate, and uterine (endometrial) cancer increases.
Treatment Management
With a BMI > 30 $kg/m^2$, the patient strictly requires corrective measures. The main non-pharmacological approach is strict dietary therapy, implying a restriction of daily caloric intake to 1200–1600 kcal. The diet also includes the introduction of fasting days 1–2 times a week.
Physical exercise must be combined with a low-calorie diet in all cases. However, when diagnosing abdominal obesity, unlike other forms, there is a strict necessity for the early initiation of drug therapy to prevent target organ remodeling.
Briefly: answers to topical questions
What degrees of obesity (I, II, III) are distinguished in the WHO classification according to BMI?
Depending on the body mass index, three main degrees of obesity are distinguished.
- Grade I obesity — BMI from 30.0 to 34.9 kg/m².
- Grade II obesity — BMI from 35.0 to 39.9 kg/m².
- Grade III obesity — BMI $\ge$ 40 kg/m².
Also, reduced threshold values can be used to assess the risk of complications, where grade I starts from 27.5 kg/m², grade II from 32.5 kg/m², and grade III from 37.5 kg/m².
What biologically active substances (adipokines) are secreted by visceral adipose tissue?
Visceral adipose tissue functions as an endocrine organ and secretes biologically active substances. These include:
- Leptin — an adipokine produced by visceral adipocytes; its synthesis increases in NAFLD, and serum leptin levels are higher in NASH than in healthy individuals.
- Adiponectin — an adipokine produced by visceral adipocytes; regulates appetite, insulin sensitivity, and inflammation; its secretion decreases in obesity.
- Interleukin-6.
- Tumor necrosis factor-alpha.
What are the pathogenesis and clinical presentation of Pickwickian syndrome?
The pathogenesis of Pickwickian syndrome is based on pronounced alveolar hypoventilation against the background of significant obesity. This leads to the development of restrictive respiratory failure, hypoxemia, hypercapnia, respiratory acidosis, as well as nocturnal apnea and arrhythmias.
The clinical picture includes:
- Respiratory manifestations — exertional dyspnea, cyanosis, apnea episodes.
- Neurological symptoms — irresistible daytime sleepiness and morning headaches.
- Cardiovascular symptoms — development of cor pulmonale, leg edema, risk of sudden cardiac death.
The term "Pickwickian syndrome" was proposed by physician W. Osler in 1928. It is easy to remember that it is named after a character from Charles Dickens's The Pickwick Papers — an incredibly stout youth who constantly fell asleep during the day.
Class and exam questions
Can obesity be ruled out if BMI is normal?
No. Abdominal obesity can also be detected at normal BMI values, which is why waist circumference measurement is mandatory.
Is it necessary to calculate the waist-to-hip ratio for diagnosis?
In modern medical practice, this indicator is no longer used. Measuring only the waist circumference is sufficient for diagnosis.
Why is drug therapy important in abdominal obesity?
Because visceral adipose tissue has high secretory activity (releases leptin and inflammatory mediators), which requires early pharmacological intervention to protect target organs.
What is the metabolic context of obesity?
This is a comparison of the presence of visceral fat with metabolic disorders: lipid disorders, type 2 diabetes mellitus, and gout.
What else to study on this topic
- Pathogenesis of obstructive sleep apnea syndrome
- Mechanisms of insulin resistance development
- The Framingham Heart Study and its role in cardiology
- Association between obesity and purine metabolism disorders (gout)
- Pathological vascular and myocardial remodeling in obesity
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