Weight changes may occur during menstruation, but whether you get heavier or lighter is related to your individual physical condition and cannot be generalized. During menstruation, women have higher levels of estrogen and lower levels of progesterone. Progesterone has the effect of promoting sodium and water excretion in the distal renal tubules, while elevated estrogen decreases the glomerular filtration rate, increases sodium absorption in the renal tubules, and causes sodium ions to be trapped outside the cells, resulting in water and sodium retention and a short period of weight gain. Normally, after menstruation, hormone levels in the body gradually stabilize, and weight will return to normal. However, some women experience symptoms such as menstrual cramps, loss of appetite, diarrhea, etc. During menstruation, gastrointestinal function is affected, which can lead to reduced dietary intake and weight loss. Even if there is a change in weight during menstruation, the change is not significant and there is no need to be overly concerned about it, just pay attention to rest and diet.