Measuring Obesity: Waist Circumference and BMI?

What standards do you think of when evaluating whether a person is obese or not, including waist circumference and BMI?

Measuring waist circumference is a simple and low-cost method that basically only requires a soft tape measure. An increased waist circumference is likely associated with an increase in total abdominal fat, but it may not be an ideal method for assessing obesity.

Firstly, this method lacks accuracy. Various factors can affect measurement results, including the position, force, timing (before or after meals), and whether the tester is holding their breath.

Secondly, this method is suitable for recording individual changes, but not for comparison with others. Different factors, including race, body frame, gender, and age, can all affect waist circumference measurements, making it difficult to compare between individuals and to establish a universal threshold.

Thirdly, an increase in waist circumference may not reflect an increase in fat. Waist circumference can also be affected by other factors, such as muscle mass, skeletal size, and whether the individual has undergone liposuction surgery.

Although waist circumference is not the ideal standard for measuring obesity, it still has reference value. Increased waist circumference is usually associated with an increase in abdominal fat (but not visceral fat), which is directly related to metabolism and fat-related diseases (including diabetes, hypertension, hyperlipidemia, cardiovascular diseases, cancer, etc.). Therefore, regularly measuring waist circumference can help understand the risk of developing these diseases.

BMI is the most commonly used method for analyzing whether a person’s weight is appropriate. The calculation method is weight (kg) / height (m)2. It is a commonly used, low-cost, and repeatable calculation method, and has become a popular tool for epidemiological research. BMI has different thresholds (including underweight, normal weight, overweight, and obese), but the standards were established without considering differences between different factors (such as race, ethnicity, and gender), and thus should not be the only standard for measuring obesity.

In addition, BMI can estimate body fat, but it cannot directly reflect body composition, such as muscle and fat content. As BMI generally increases with weight gain, weight gain can be due to an increase in muscle or fat mass. Therefore, BMI results may have errors: for example, muscular individuals may be misdiagnosed as obese, while patients with decreased muscle mass may not be diagnosed with obesity.

Similarly, BMI can also provide information related to disease risk. An increase in BMI is usually associated with the risk of metabolic and fat-related diseases, and the correlation with these diseases is even greater than that of waist circumference measurements. Regularly measuring and recording BMI and waist circumference can help individuals better understand their risk of developing metabolic and fat-related diseases.