1. The BMI (Body Mass Index) formula calculates the body's weight-to-height ratio by dividing weight in kilograms by the square of height in meters, represented as BMI = weight(kg) / height(m)^2.2. The Body Mass Index is an international standard used to measure an individual's weight in relation to their height, assessing whether a person falls within a healthy weight range.3. According to Chinese standards, a normal BMI range is 18.5 to 24.9 kg/m^2. A BMI of 24 to 27.9 kg/m^2 is considered overweight, while a BMI of 28 kg/m^2 or higher is classified as obese. Conversely, a BMI less than 18.5 kg/m^2 is considered underweight.4. However, BMI does not provide detailed information on the distribution of body fat nor distinguish between muscle and fat content, which may lead to misinterpretations of health status.5. To obtain a more comprehensive assessment of health, the following methods can be combined: 5.1 Ideal Weight: Calculated by subtracting 105 or 100×0.9 (for males) or ×0.85 (for females) from the height in centimeters. The normal range for ideal weight is ±10%, with overweight defined as more than 10%-19.9% and obesity as more than 20%. 5.2 Waist Circumference: Measured in an upright position, with feet apart 25-30cm, the measurement taken at the midpoint of the line between the anterior superior iliac spine and the lower border of the twelfth rib. Normal waist circumference for males should be less than 85cm, and for females, less than 80cm. 5.3 Waist-to-Hip Ratio: Measured by wrapping a tape measure around the hips at the widest point and comparing it to the waist circumference. For males, the waist-to-hip ratio should be less than 0.9, and for females, less than 0.85. 5.4 Imaging Tests: Such as CT or MRI, can be used to confirm body fat levels and assess the distribution of intra-abdominal fat. 5.5 Other Methods: Dual-energy X-ray absorptiometry (DXA), bioelectrical impedance analysis, etc., can also be used to comprehensively determine body fat content and evaluate health status.6. Being underweight or overweight is detrimental to health. Individuals who are underweight should aim to improve their condition by increasing muscle mass, consuming adequate amounts of high-protein, quality fats, and high-calorie foods (such as meat, eggs, etc.), and maintaining a balanced diet.7. Those who are overweight can reduce weight through methods such as exercise (yoga, jogging, swimming, walking), adjusting dietary patterns, and controlling calorie intake.