1. Basal metabolism
Basal metabolic rate is the metabolic rate measured in a very quiet environment, in a waking state, when a person’s body is not affected by mental tension, muscle activity and ambient temperature, etc., excluding other influencing factors as far as possible.
In daily life, basal metabolism is easily influenced by other factors, such as ambient temperature, hormones, age, gender, height, and genetics.
The basal metabolic rate is lowest when the ambient temperature is between 20 and 25°C. The metabolic rate increases in both low and high-temperature environments. Nowadays, people live in constant temperature rooms for a long time, with less energy consumption, and it is easy to gain weight.
Hormones are also an important factor affecting basal metabolism. For example, people who are mentally stressed consume more energy than those who are in a relaxed mood, so we see that people who are particularly stressed all day long tend to be thinner.
In addition, men have a higher basal metabolic rate than women, taller people have a higher basal metabolic rate than smaller people, and there is a certain genetic tendency for the basal metabolic rate to be higher or lower.
People who use computers all day and do not go out to exercise consume much less energy than workers. Even if you go out and exercise every day, the energy expended will vary depending on the exercise program and duration.
Whenever I ask patients about their diet, I ask about the amount of exercise, including the nature of their work at work, whether they do housework at home, whether they exercise outdoors every day and the program and duration of exercise.
If the patient says, “I walk for one hour every day.” I would have to ask more carefully: “Did you walk fast during the walk? Did you sweat?” Because the difference in energy consumption between “brisk walking” and “walking” in one hour is too great.
3. Food digestion
The process of digesting food also uses energy, which is known as the kinetic effect of food.
The kinetic effect is different for different nutrients. Protein has the largest kinetic effect, about 30%, while carbohydrates and fats have a lower kinetic effect, basically around 5%.
For example, if you eat 100 kcal of protein and use 30% of it for digestion and decomposition, 70 kcal is actually absorbed into the body. In contrast, when 100 kcal of carbohydrates enter the body, only 5% of the digestion and decomposition itself is used, and what is absorbed into the body is about 95 kcal and the same amount of fat.