The corollary to PMS-related bloating is often weight gain. A survey of more than 1,500 women found that about one in two experience bloating or weight gain during their cycle. In general, women with PMS report gaining anywhere between three to ten pounds during their premenstrual phase. The reasons for this are complicated.

First, some weight gain is genuinely caused by fluid retention, common symptom of PMS. However, while women only gain a small amount of weight—between one and three pounds, for example—they are also plagued with all of the discomforts of bloating, such as feelings of skin tightness and heaviness. So how they experience their weight gain is exaggerated. These bloating-related discomforts may lead women to perceive they’ve gained more weight than they actually have, so the woman who has gained three pounds may feel as though she’s gained ten pounds.

Weight gained as a result of fluid retention, or water weight, usually temporary and the pounds come off as the woman gets her period or shortly thereafter.

Second, many women who have PMS or are diagnosed with PMS are older and as women age, their metabolism slows. A slower metabolism makes it harder to burn calories. Consequently, a poor diet, or PMS-induced cravings for sugary foods and other carbohydrates, may lead to quicker weight gain and an overall perception that weight gain is related to PMS, when it's actually related to eating habits.

Third, many women who suffer from PMS are prone to stress, and stress is a known trigger for overeating, which can lead to weight gain.

Finally, many of the foods that women crave while they’re (e.g., chocolate, dairy, or salty snacks) can produce excess cause the body to retain water, and cause bloating. Indulging foods ends up intensifying both the actual weight gain itself perception of that weight. It’s a vicious cycle: stress, food cravings, and the hormonal processes that trigger bloating cause women gain weight, eat more, and feel worse.