Degrees of obesity

A common feature of all forms of obesity is the excessive accumulation of adipose tissue in the body. To diagnose obesity and determine its degree, the body mass index (BMI) is used, which is obtained from the ratio of body weight (in kilograms) to height (in meters) squared:

BMI - Body weight (kg) Height (m) ²

A BMI in the range of 18.5-24.5 kg/m2 ^corresponds to normal body weight.

Classification of obesity by BMI (WHO, 1997)

Body weight types	BMI kg/ m2	Risk of concomitant diseases
Underweight	<18.5	Low (increased risk of other diseases)
Normal body weight	18.5-24.5	Ordinary
Overweight (pre-obesity)	25.0-29.9	Increased
Obesity stage I	30.0-34.9	High
Obesity stage II	35.0-39.9	Very tall
Obesity stage III	>40,0	Extremely high

The BMI indicator is not reliable for children with an unfinished growth period, people over 65 years old, athletes and people with very developed muscles, and pregnant women.

The BMI indicator is used not only to diagnose obesity, but also to determine the risk of developing obesity-related diseases and to determine treatment tactics for obese patients.

The distribution pattern of adipose tissue is determined by the waist circumference/hip circumference (WC/HC) ratio. WC/HC for men >1.0 and women 0.85 indicates abdominal obesity. Recent studies have shown that a reliable indicator of excess accumulation of adipose tissue in the abdominal area is waist circumference with a BMI<35. Waist circumference is also an indicator of the clinical risk of developing metabolic complications of obesity.

Waist circumference and risk of developing metabolic complications (WHO, 1997)

	Increased	High
Men Women	>94cm >80cm	>102 cm >88cm

Examination of patients, along with determination of anthropometric parameters, includes measurement of blood pressure, ECG examination, skull radiography, determination of levels of total cholesterol, low- and high-density lipoproteins, triglycerides, fasting glucose or glucose with a standard glucose tolerance test, fasting insulin, LH, FSH, PRL, E2, TSH, free T4 (as indicated).

Differential diagnostics of obesity. Clinical and laboratory signs of increased activity of the hypothalamic-pituitary system (skin changes, redistribution of subcutaneous fat, arterial hypertension, excess urinary excretion of free cortisol) in patients with hypothalamic obesity often complicate diagnostics, since similar symptoms may be present in patients with hypercorticism. In these cases, along with X-ray of the skull and spine, determination of urinary excretion of free cortisol, and the content of cortisol in plasma during the day, a small test with dexamethasone is carried out: dexamethasone is prescribed at 0.5 mg (1 tablet) every 6 hours for two days. To determine the content of free cortisol in urine, its daily amount is collected before the test and on the 2nd day of the study. In patients with hypothalamic obesity, the excretion of free cortisol against the background of dexamethasone decreases by at least 50% of the initial value. In hypercorticism, this indicator does not change.

Higher than normal plasma ACTH and cortisol levels and some increase in urinary free cortisol excretion found in patients with hypothalamic syndrome of puberty necessitate differential diagnosis with Itsenko-Cushing's disease or syndrome and hypothalamic syndrome of puberty. High growth, accelerated physical and sexual development, skeletal differentiation, absence of osteoporosis of the cranial and spinal bones, normal daily rhythm of cortisol secretion, positive reaction (based on urinary free cortisol excretion) to the administration of small doses of dexamethasone allow us to reject the diagnosis of hypercorticism.

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