Scientific diagnosis of simple obesity: exclusion of secondary obesity and grading standards

Diagnosis of Simple Obesity

1. Simple Obesity vs. Secondary Obesity

Obesity is a symptom of a disease, called secondary obesity or symptomatic obesity. Obesity without a clear cause is called simple obesity. Diagnosis of simple obesity requires ruling out secondary obesity through medical history, physical examination, and laboratory tests.

Diseases that can cause secondary obesity:

(1) Hyperinsulinemia: Insulinemia caused by islet cell tumors, the use of exogenous insulin, and certain drugs can all lead to obesity.

(2) Excessive Glucocorticoids: Cushing's syndrome of various causes and the use of exogenous glucocorticoids can all cause obesity, typically manifested as central obesity.

(3) Other endocrine diseases: Type II diabetes is often accompanied by obesity; polycystic ovary syndrome, hypogonadism, and hypothyroidism can all cause obesity. (4) Some genetic diseases can cause obesity, such as Laurence-Moon-Bardet-Biedl syndrome, Alstrom syndrome, Prader-Willi syndrome, Down syndrome, etc.

2. Degree of Obesity: A measured weight exceeding the standard weight by more than 20% is considered obese; 20%–30% is mild obesity; 30%–50% is moderate obesity; >50% is severe obesity; and >100% is morbid obesity.

Morbid obesity: BMI >25 kg/m² is obese; BMI 25–29.9 is Grade I obesity; BMI 30–39.9 is Grade II obesity; and BMI >40 is Grade III obesity.

3. Classification of Obesity: Studies have shown that the distribution of body fat is closely related to metabolic disorders and increased morbidity and mortality. Data from the United States in 1984 showed that the type of fat distribution in obese individuals was a more predictive factor for the incidence of diabetes than the degree of obesity. Under the same degree of obesity, those with abdominal obesity had a 3-5 times higher risk of myocardial infarction and stroke.

Obesity types can be diagnosed using indicators such as waist circumference, VIS ratio, and visceral fat index measured by ultrasound: visceral obesity and subcutaneous obesity. Patients with visceral obesity have significantly higher rates of complications such as coronary heart disease, diabetes, and fatty liver than those with subcutaneous obesity.

4. High-Risk Groups
According to the recommendations of the National Institutes of Health (NIH), the following groups are considered high-risk and require special attention to weight control:

(1) BMI > 30 kg/m² or BMI of 25-30 kg/m² with abdominal fat distribution or two or more obesity-related complications.

(2) Waist circumference > 88 cm for women and > 102 cm for men.

(3) Individuals with existing obesity-related complications such as non-insulin-dependent diabetes mellitus, hyperlipidemia, and hypertension.

(4) BMI > 25 kg/m² combined with risk factors such as smoking.

5. Obesity requiring surgical treatment
Some obese patients cannot control their weight simply by controlling their diet and increasing physical activity, and surgical treatment may be considered. For patients with BMI ≥ 40 kg/m², gastric volume restriction surgery is an effective treatment. Surgical treatment is generally limited to patients with BMI ≥ 35 kg/m².