In a few days. According to Xiaohe's medical code, the weight gain after climbing the mountain is mainly due to the accumulation of water and muscle glycogen, which usually returns to normal within a few days, so it can be recovered within a few days. Mountain climbing is an aerobic exercise, which consumes a lot of energy in the process. In order to replenish energy, the body will absorb more water and increase the storage of muscle glycogen, leading to weight gain.