Calorie (Cal for short), transliterated from English Calorie, is defined as the heat required to raise 1 gram of water to 1 degree Celsius at 1 atmospheric pressure; Calories are energy units and are still widely used in nutrition measurement and fitness manuals. The international standard unit of energy is joule.

Just as computers consume electricity and trucks consume oil, so do human daily activities. Heat not only provides energy for people's exercise, daily work and life, but also provides energy for human life activities, blood circulation, breathing, digestion and absorption. People who lose weight can burn fat through exercise, which can accelerate calorie consumption and achieve the goal of healthy weight loss.

Generally speaking, adults need at least 1500 kcal of energy every day to maintain body function, because even if you lie still, your body still needs energy to maintain body temperature, cardiopulmonary function and brain operation. Basal metabolic consumption varies with individual height, weight, age and gender. Human survival needs energy, which is obtained from food. The calorie content in food is a measure of how much potential energy food produces. 1g carbohydrate contains 4 calories, 1g protein contains 4 calories, and 1g fat contains 9 calories. Food is generally composed of these three substances. Therefore, as long as we know the contents of these three substances in food, we can know how much heat or energy food contains.