Before the onset of menstruation, weight may increase mildly, but the increase will not be significant. Before the onset of menstruation, both estrogen and progesterone levels are reduced to their lowest levels, and the decrease in estrogen may cause edema in women’s bodies, leading to water and sodium retention, which may slightly affect weight gain. A decrease in progesterone leads to a decrease in a woman’s basal metabolic rate. With a lower basal metabolic rate, gastrointestinal motility slows down and food stays in the digestive tract for longer periods of time, and women may become constipated or bloated, which can also increase their weight. The combination of these two conditions can lead to edema, weight gain, abdominal pain, bloating and constipation before menstruation, which can usually decrease or disappear quickly after menstruation.