Five factors affecting basal metabolic rate and calculation of daily calorie requirements

What are the most common factors affecting basal metabolic rate? First, physical factors. As mentioned above, patients with hyperthyroidism experience increased heat production, leading to an increased basal metabolic rate, while those with hypothyroidism experience a decreased basal metabolic rate. Second, muscle activity. During muscle activity, the heat generated by bones can increase several times, accounting for 75% to 80% of total heat production. The degree of increase is related to the intensity of muscle activity. For example, walking increases heat production by about three times compared to a resting state, while vigorous exercise can increase it by 10 to 20 times. During demanding mental work, the body can increase skeletal muscle tone and adrenal gland activity through neural pathways, also increasing heat production. Third, the specific dynamic effect of food. For a period after eating, the body produces an additional amount of heat compared to before eating. Protein foods can increase heat production by 30%, while carbohydrates or fats can increase it by 4% to 6%. When consuming a typical mixed diet, daily heat production increases by 600 to 800 kJ due to food intake. The mechanism behind this phenomenon is not yet fully understood. Fourthly, ambient temperature. Human energy metabolism is most stable in a natural environment of 20-30℃. Temperatures above or below this range, especially during seasonal transitions, increase heat production. For example, when the body is exposed to cold, it reflexively increases muscle tension first, followed by shivering. Shivering is a small, rhythmic contraction of skeletal muscles. Its characteristic is that both extensor and flexor muscles are active simultaneously, making external work almost impossible. All the energy consumed is converted into heat, with a maximum heat production rate of 39.2 kJ/kg per minute, making the body's heat production 4-5 times higher than usual. Heat production also increases when the temperature is 30-45℃ due to the increased rate of chemical reactions within the body. Fifthly, the activity of endocrine glands. As mentioned above, thyroid hormones promote enhanced oxidative metabolism, and adrenaline also enhances intracellular oxidation reactions, simultaneously increasing blood glucose concentration and utilization, thus increasing heat production.

Now that we know about basal metabolism and basal metabolic rate, what is their relationship with calories? Basal metabolic rate is the minimum amount of energy consumed by vital organs in the body to function, and it gradually decreases with age. A high basal metabolic rate indicates youthful bodily function and high energy expenditure; conversely, a low basal metabolic rate indicates reduced energy expenditure and declining bodily function. The healthiest and most effective way to increase basal metabolic rate is through exercise and a balanced diet, while also increasing muscle mass. For those who need to control body fat percentage or want to lose weight, the first step is to reduce calorie intake while maintaining a balanced diet, and then find ways to increase muscle mass and raise basal metabolic rate. Once you have a correct basal metabolic rate, you can estimate your daily calorie expenditure based on this value and your daily work intensity. Then, based on your daily expenditure, you can determine your daily food intake. When on a weight loss plan, your daily calorie intake should be less than your daily calorie expenditure. For example, if a person reduces their daily calorie intake by 500 calories, they can reduce their intake by 15,000 calories per month, which is approximately 2 kilograms of weight loss. Therefore, understanding the concept and principles of basal metabolic rate (BMR) is fundamental to any weight loss plan and a crucial step in measuring a dieter's success. BMR determines the majority of the body's calorie expenditure; thus, people with low BMRs will suffer significantly during weight loss. As we know, BMR accounts for approximately 70% of the body's total calorie expenditure, making it the most significant calorie burner. Therefore, a high or low BMR affects the speed and effectiveness of weight loss. In other words, people with low BMRs are more prone to obesity. If they rely solely on dieting, those with low BMRs will still gain weight even if they eat very little due to insufficient metabolism. Therefore, increasing BMR is a crucial step in avoiding common weight loss misconceptions.

In life, we often see people who eat a lot and don't watch their diet, yet they don't gain weight. However, some people eat little but easily accumulate fat, their weight constantly increasing – the kind of person who seems to gain weight even from drinking water. The key is that we consume more calories than we need each day, and we don't have enough energy to metabolize the excess. Therefore, it can only be converted into fat and stored in your body. So, to lose weight, you need to target your calorie intake and manage your calorie expenditure effectively.

We already know the meaning of basal metabolism and how to calculate basal metabolic rate, meaning we already know how calories are expelled. Controlling calorie intake and expenditure is crucial. To manage calorie intake and expenditure effectively, we should also learn to calculate our daily calorie needs. In reality, everyone's daily calorie needs vary depending on their work type and lifestyle. Therefore, to know your calorie needs, you need to choose a suitable calculation method based on your lifestyle. Here is a set of work-life type values ​​(coefficients): ① People who sit in the office or classroom for long periods, rarely exercise, or don't exercise at all (1.2); ② People who occasionally exercise, take walks, go shopping, or go on outings, exercising a small amount 1-3 times a week (1.3); ③ People with a consistent exercise habit, or who go to the gym, exercising 3-5 times a week (1.5); ④ People who love sports, exercising 6-7 times a week, or people with a heavy workload, such as those engaged in physical labor (1.7); ⑤ People whose work or lifestyle requires a lot of physical labor and consumes a lot of energy, such as athletes (1.9). This value will be used in the following calorie requirement calculation methods.

The method we introduce for calculating daily calorie needs is: Daily Calorie Needs = Basal Metabolic Rate (BMR) × Work-Life Type Value (coefficient). Let's illustrate this with an example: Mr. Jia's BMR is 1898.8 calories. He regularly exercises and runs three days a week, and his workload isn't heavy, so he chooses 1.5. Therefore, his daily calorie need = 1898.8 × 15 = 2848.2 calories. Ms. Liu's BMR is 1364.8 calories. She spends long hours sitting in front of a computer and rarely exercises, so she chooses 1.2. Therefore, her daily calorie need = 1364.82 × 1.2 = 1637.76 calories. Based on the calculated calorie intake, you can know how many calories you should consume each day. If you consume too many calories, you should choose to exercise to burn them off, thus preventing an increase in body fat percentage.

There are three main ways the human body burns calories: diet, physical activity, and basal metabolic rate (BMR). BMR plays a crucial role in this process. If you want to lose weight, it's more practical to increase your BMR than to painstakingly restrict your diet. This will not only help you achieve your ideal weight but also give you a youthful glow.