5 reasons for possible weight gain during your period

Do you find it hard to lose weight your period? If so, you're not alone. We explain why your scales may read a little differently during your time of the month.
Published 29 August, 2018

The feeling that your period may cause weight gain and even prevent you from losing weight isn’t all in your head.

In fact, there are several physiological and psychological reasons why menstruation adds pounds that may last longer than the week of your period. The good news? With some knowledge of the why and how, you don’t need to grin and bear it. Here’s what you need to know:

1. Fluid retention

Feeling bloated is a common complaint during the menstrual cycle, when elevated levels of female reproductive hormones oestrogen and progesterone lead to a shift in the body’s set point for sodium and cause fluid retention. Specifically, the part of your menstrual cycle you can 'bloat-blame' is the so-called luteal phase, which begins after ovulation and lasts for around two weeks. At the beginning of this phase oestrogen drops, then rises, then remains high. Progesterone levels also run high.

This hormonal upheaval can cause problems with the digestive tract. Oestrogen can cause water retention, leading to bloating (which definitely feels like a barrier to weight loss), while progesterone results in delayed GI (gastrointestinal) transit time. This means that food moves more slowly through the intestine, resulting in constipation and bloating. Then, when progesterone levels drop and bleeding begins, you might experience increased bowel activity, potentially leading to diarrhoea and...you guessed it, bloating!

2. Constipation

Your period affects how well your gastrointestinal tract works to eliminate waste from your body. "Progesterone causes some relaxation of smooth muscle, leading to a reduction in gastrointestinal motility, which may lead to bloating and constipation in some women,” says Dr. Heather Huddleston MD. To reduce both and give potential weight loss a helping hand, increase the amount of fibre in your diet, particularly during the second half of your cycle, she suggests.

3. Food intake

Progesterone plays another weighty role during the second half of the menstrual cycle, by increasing appetite.  Your body uses more calories leading up to and during your period. Burning more calories increases your basal metabolic rate (the rate at which the body uses energy while at rest), and as a result you feel hungry more often. These hormones also make you crave comfort foods like chocolate and biscuits - which are exactly the things you should steer clear of, as well as caffeine and salty foods.

Did you know your body burns an extra 100-300 calories for a few days before and/or during your period? So the trick is not to overindulge and sabotage your healthy eating weight loss plan during your period. “Consistent overeating that is not offset by an increase in physical activity can lead to permanent weight gain,” says Dr. Huddleston.

4. PMS

Premenstrual syndrome, or PMS, begins about one or two weeks before a period starts. A study of 259 healthy women with regular menstrual cycles showed significant increases in appetite, protein intake, and total cravings, including those for chocolate, sweets, and salty flavors during the luteal, or premenstrual, phase before menstruation begins.

Experiencing depression or anxiety are also hallmarks of PMS, which is thought to be caused by cyclic changes in the brain chemical serotonin. “For some women, these mood symptoms can also lead to increased food intake,” says Dr. Huddleston. See a health professional if you experience significant depression or anxiety during PMS, says Dr. Huddleston, as they can be associated with binge eating or eating disordered behaviors. To offset the barriers to losing weight during PMS or the second half of your cycle, try increasing acitivity and focus on consuming healthy, nutrient-rich foods.


If you experience irregular periods and weight gain, there may be cause for concern. Polycystic Ovary Syndrome, or PCOS, is an imbalance of reproductive hormones that causes metabolism problems. It affects one in 10 women of child bearing age.

In obese women with PCOS, losing weight may help regulate their menstrual cycles. “Fat itself can produce oestrogen which can cause hormonal imbalances that can affect the cycle,” says Dr. Stephens. “Irregular cycles do not cause weight gain. Weight gain can cause irregular cycles.”

But lets end on a positive note. For most women, weight gain during menstruation is only temporary. Maintaining an overall healthy lifestyle and diet will with weight loss and ensure those fluctuating pounds are not a permanent feature.