The modern concept views obesity as a chronic, progressive, and relapsing disease that reduces quality and length of life.

Classification of obesity and its association with premature mortality risk
The classic WHO classification is based on body mass index (BMI):
- Normal: <25 kg/m²
- Overweight: 25–29.9 kg/m²
- Obesity: ≥30 kg/m²

However, in older adults, BMI overestimates muscle mass and underestimates fat mass, reducing diagnostic accuracy. In a study of 4,800 adults aged 40–80, the optimal threshold for diagnosing obesity was BMI ≥27.3 kg/m², which better reflects actual fat mass and the risk of age-related diseases.

Main types and criteria:
General obesity — defined by BMI ≥30 kg/m², reflects overall excess body weight but is not always associated with metabolic risks.

Abdominal obesity — assessed with a measuring tape by waist circumference and waist-to-hip ratio (WHR), reflects fat accumulation in the abdominal cavity.
Norms:
Women >0.85, Men >0.9

Visceral obesity — a key pathogenetic type, characterized by visceral fat area (VFA) ≥100 cm² according to CT or bioimpedance analysis.

Modern classification relies on functional and morphological criteria:
1️⃣ By fat location:
- Subcutaneous, visceral, ectopic (liver, pancreas, muscles).
2️⃣ By metabolic profile:
- Metabolically healthy obesity and unhealthy obesity.
3️⃣ By combination with other tissue disorders:
- Visceral obesity + muscle weakness (sarcopenic obesity);
- Visceral obesity + myosteatosis (fat infiltration of muscles).

Practical significance
- BMI assessment is a foundation but insufficient for risk evaluation: patients with normal weight but a high proportion of visceral fat have a high risk of metabolic and vascular complications.
- Measurement of visceral fat (VFA ≥100 cm²) is a key diagnostic criterion for visceral obesity.
- Comprehensive assessment of weight problems should include blood lipid profile, diabetes diagnosis, thyroid disease, atherosclerosis, muscle mass indicators, and functional tests (handgrip strength).

@drakarasev