The energy supply of human body can not be completed by any organ, and it needs the close cooperation of multiple systems. The respiratory system inhales oxygen and discharges carbon dioxide; The digestive system ingests nutrients (energy substances) and discharges residues; Blood transports oxygen and nutrients to all parts of the body. There is also the participation of urinary system, nervous system and endocrine system. Energy substances (sugar, fat, protein) are decomposed in cells, releasing energy. According to the adequacy of oxygen, there are two ways to decompose energy substances: aerobic oxidation and anaerobic decomposition. In the process of aerobic oxidation, energy substances are completely decomposed and harmful substances (lactic acid) are not produced.

Only when the sugar in the body is basically used up can the body use fat oxidation for energy supply. So all the weight-loss exercises use aerobic exercise, which lasts for more than an hour.

Both fitness running and weight loss exercise belong to aerobic exercise, that is, the exercise intensity is not great, and the inhaled oxygen can be used by the body.

The energy supply of the human body involves a wide range, and it is impossible to say it clearly in three or five sentences.