All daily food, except water, supplies calories, which are needed by our body, and nowadays all calories are calculated in calories. A calorie is the calorie used to make the temperature of one kilogram of water rise by one degree Celsius. The body needs calories for three main purposes: 1, to maintain the body’s basal metabolism. For example, to maintain our breathing, digestion, nutrient absorption and other tissue activities in the body. 2, our activities need calories, such as walking, standing, sitting, running and so on every day, simply put, every action needs calories. People with high activity need higher calories, such as physical labor old, while clerical workers need less calories. 3. Calories are needed for growth, so developing children, teenagers, pregnant women and lactating women need more calories. The speed of basal metabolism varies from person to person, but there are some factors that affect its speed, and here are some of them 1. Age: Young people have a higher basal metabolic rate than older people. The basal metabolism is faster in childhood, slightly flattened after about five years of age, then accelerated again in adolescence, and then slowed and receded in adulthood, and the slowest in old age. These are due to the growth period, the establishment of protein in the body and metabolic rate is faster, and affect the increase in the basal metabolic rate. 2, gender: women’s basal metabolism is lower than that of men, mainly because women’s body fat is higher than that of men. If men and women have the same weight, women’s body fat may be 10% or more higher than men’s. Basal metabolism is based on muscle activity in the body, and because women have less muscle in their bodies than men, their basal metabolism is lower. If you calculate only the muscle activity in their bodies regardless of gender, their basal metabolism is supposed to be the same. 3, the weather: colder weather will usually increase the basal metabolic rate, because the body needs higher heat to maintain body temperature. But why many people will gain weight in the winter, mainly because of less activity, or eat more food. For example, in winter, many people like to eat hot pot, barbecue or engage in a large food meeting, etc., the calories of these foods are higher than the general summer food. 4, body shape: taller people have a higher basal metabolic rate, because the body’s muscle mass, relatively more than those with small bodies, and muscle activity will affect the basal metabolism. 5, the role of heat production: after we eat, the body’s basal metabolism will automatically increase, the body consumes more calories. The highest basal metabolism is about an hour after eating, and then slowly decreases until two hours later to normal. For this reason, some people are in favor of eating small meals to consume calories in the body. But this has little effect on the basal metabolic rate, so the role in weight loss is not significant, but certainly better than eating only one meal a day. 6, exercise: the body’s basal metabolism will increase after exercise, but the medical community has not been able to understand why. In the 12 to 18 hours after exercise, the basal metabolism is still higher than usual. People in general do not like to do exercise, for the health of the body, is not ideal. 7. Special period: During pregnancy and breastfeeding, the basal metabolism will be accelerated, mainly due to the construction and metabolism of protein in the body is faster than usual. The basal calories for adults is about 1200 Kcal, general life, (no physical work, sports) need 2000 Kcal a day.