Weight gain before menstruation may be a manifestation of sodium retention, increased diet and decreased exercise. 1. Sodium retention: Before menstruation, the level of progesterone or estrogen may reach its peak, and progesterone may cause sodium retention, which may lead to idiopathic edema in women, which may cause weight gain. 2. Increase in diet: Before menstruation, the hormone level changes in the body, which may cause an increase in appetite, eating more, may cause weight gain. 3. Decrease in exercise: Before menstruation, female patients have obvious changes in mood, lying down for a long time without exercise, which may lead to weight gain. It is recommended that those with abnormal menstrual discomfort consult a specialist.