How to accurately calculate basal metabolic rate to aid in scientific weight loss
What is your basal metabolic rate?
Many people know about basal metabolic rate. Thanks to the extensive promotion by weight loss enthusiasts, many also believe that people with a slow basal metabolic rate find it difficult to lose weight. Let's set aside the question of whether this statement is accurate; what I want to say is that most people don't know how to calculate their own basal metabolic rate, let alone how to scientifically increase it.
There are many methods for calculating basal metabolic rate. For example, in medicine, a basal metabolic rate analyzer is used to measure an individual's oxygen consumption (O2L/h) per unit time. The basal metabolic rate is then calculated using the formula BMR = O2L/h × 19.3kJ ÷ S, where S is body surface area.
The method for calculating body surface area is: S = W × 0.245 × H × 0.725 × 71.84; where W is weight (kg), H is height (cm), and 71.84 is a coefficient.
In this calculation method, to exclude the extra energy expenditure caused by muscle work, mental activity, food digestion, and thermoregulation in response to external temperature changes (called functional expenditure), the subject must remain absolutely still and fast (12-18 hours without food). The energy expenditure at the critical temperature is used as the basal metabolic rate.
In Japan, the basal metabolic rate of an average adult is 1200-1400 kcal, while in Europe and America, it is 1500-2000 kcal. However, due to differences in lifestyle and other factors, this value is not absolute. Basal metabolic rate inevitably includes the energy expenditure of organs such as the heart, respiratory muscles, digestive tract, and vascular smooth muscle, as well as functional expenditure caused by the secretory activities of the liver and kidneys.
Because this calculation method is relatively complex and inconvenient for daily use, a simpler formula has been developed to calculate each individual's basal metabolic rate.
Female basal metabolic rate = 661 + 9.6 × weight (kg) + 1.72 × height (cm) - 4.7 × age
Male basal metabolic rate = 67 + 13.73 × weight (kg) + 5 × height (cm) - 6.9 × age
For example, if Dr. Qiu is 18 years old, 1.78 meters tall, and weighs 65 kg, then his daily basal metabolic rate is 67 + 13.73 × 65 + 5 × 178 - 6.9 × 18 = 1726.55 kcal. This formula is relatively simple to use, but it has a problem: it only considers the test subject's height, weight, and age, but not their body composition. People of the same height and weight can have significantly different basal metabolic rates due to variations in body "firmness," fat and muscle content, sometimes by as much as thousands of kilocalories.
Therefore, I personally often recommend using a third measurement method: a body fat scale. The basic principle of a body fat scale is "bioelectrical impedance analysis," or BIA. It analyzes the different electrical conductivity of body fat and muscle tissue.
As we all know, fat contains very little water and is mainly composed of oil, so its electrical resistance is relatively high. Conversely, the body stores a large amount of water in lean tissues such as muscle, resulting in lower electrical resistance.
The BIA method involves placing several electrodes on the body surface. These electrodes emit a weak current into the body, and the electrical impedance value is measured. Based on this impedance value, a formula is used to calculate the specific weight of various body components. The biggest advantage of using a body fat scale is that it offers convenience and speed while maximizing measurement accuracy. To obtain more accurate data, we can drink a glass of warm water after waking up in the morning for three consecutive days, rest for a while, and then weigh ourselves. We can then take the average of these three days as our basal metabolic rate. Alternatively, we can measure our basal metabolic rate from evening until before dinner.