Basal Metabolic Rate (BMR)

BMR, as the name implies, is the rate of "basal metabolism" of the body. So, what is basal metabolism? It is the minimum energy required to maintain the body's normal life activities for a day. To put it simply, it's the energy a "vegetative person" consumes lying in bed for a day without eating, drinking, or moving. BMR is the speed of these basal metabolic activities, generally measured in units such as energy/unit surface area/unit time (e.g., KJ/m²/hour) or energy/time (e.g., Kcal/day), with Kcal/day being more commonly used.

Accurate Measurement of BMR

The most accurate way to measure BMR is through the "indirect calorimetry" method, where the subject is usually required to fast overnight (about 12 hours) and then lie down to rest for measurement the next day. The subject must be in a comfortable state and free from stress, medication, or any other stimuli that might increase metabolic activity. Additionally, the BMR measurement room must be quiet, temperature-controlled, and free from distractions. The subject needs to stay in the lab for a whole night, which is essentially being "locked in a dark room," making the process quite painful. Therefore, many researchers consider using Resting Metabolic Rate (RMR) as a substitute for BMR. The measurement method and environment for RMR are the same as BMR, but RMR subjects can sleep at home and then travel to the lab (without any strenuous physical activity). After a rest period, the measurement is taken. This process is more relaxed than measuring BMR, and the difference between BMR and RMR values is usually less than 10%.

Body Mass Index (BMI)

BMI, or Body Mass Index, is a measure calculated by dividing a person's weight in kilograms by the square of their height in meters. It is currently an internationally common standard for measuring a person's degree of fatness and health. BMI is primarily used for statistical purposes, providing a neutral and reliable indicator when comparing and analyzing the health impact of weight on individuals of different heights. However, BMI has its limitations. It is suitable for the general population but not for certain groups like athletes or fitness enthusiasts, who may have higher muscle mass than average, resulting in a higher BMI. Additionally, BMI does not reflect specific health conditions.

Body Fat Percentage

Body fat percentage refers to the ratio of fat tissue mass to total body weight, primarily consisting of subcutaneous and visceral fat. Compared to BMI, body fat percentage better indicates a person's "fatness." Being overweight does not necessarily mean being fat; high body fat percentage does. Moreover, low body fat percentage does not necessarily indicate good health; it only proves you are "thin" and nothing else. The normal range for body fat percentage in Asian women is typically between 13% and 30%, while for men, it is between 7% and 25%.

There are several methods to measure body fat percentage, including "underwater weighing," "bioelectrical impedance analysis," and "skinfold thickness measurement." The underwater weighing method, fully known as "hydrostatic weighing," is recognized as one of the most accurate methods for measuring body composition. It is based on the Archimedes principle to infer the relative fat content of the body.

Muscle Mass

The body weight can be divided into fat-free mass and fat mass. Muscle content is part of the fat-free mass, excluding about 4%-6% of the body weight as inorganic matter. Muscle is beneficial; the greater the muscle mass, the higher the basal metabolic rate, making it less likely to gain weight.

Body Water Percentage

Body water percentage refers to the percentage of water in the body weight. This data is closely related to muscle mass since muscles contain a large amount of water (about 70%). This indicator can reflect whether the weight loss method is correct. If the body water percentage decreases, it not only harms health but also increases body fat percentage.