It’s important to note, however, that if you’re experiencing weight gain in combination with irregular periods, then you could be suffering from an...

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Common PMS symptoms
Why can PMS cause weight gain?
Tips to help reduce period weight gain
When weight gain might not be a normal PMS symptom
The final say
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Women's Health

Have you ever felt heavier or more bloated just before or during your period? Well, it’s not just in your head. The fact is that, throughout the menstrual cycle, it’s thought that you can add on extra pounds that weren’t there before.^1-3

In fact, a recent study in 2023 found that women during their menstrual cycle had a weight gain of 0.5kg compared to the first week of their menstrual cycle. Extracellular fluid retention has been noted by researchers to be a potential cause for this weight gain.⁴

But don’t worry – researchers believe it’s completely normal for your weight to fluctuate throughout your cycle. Weight gained just before or during your period isn’t permanent weight gain and it isn’t usually anything to worry about.¹

Normally, you’ll gain some weight in the couple of days before your period begins. This will then come off naturally over the first few days of your period.¹

Here, we explore the reasons for weight gain and what you can do to minimise those uncomfortable bloated feelings.

Common PMS symptoms

Premenstrual syndrome (PMS) is the name for the symptoms people who menstruate might experience in the weeks leading up to their period.⁵

Some people don’t experience any adverse symptoms at all, in which case they wouldn’t be considered to struggle with PMS. It’s also perfectly normal to struggle with PMS symptoms some months, and not others – or for your PMS symptoms to vary from month to month. Overall though, PMS is a common problem among people who menstruate.^5,6

lady in orange coat and green hat with smiling expression

PMS begins about a week or so before your period starts, and involves a number of uncomfortable symptoms, such as:^5,6

mood swings
irritability
food cravings
acne
breast tenderness
bloating
weight gain

Why can PMS cause weight gain?

As if you don’t have enough to deal with on your period, adding an extra week of PMS symptoms into the mix can make you feel like you’re on a mental and physical rollercoaster.

As every body is different, weight gain during PMS differs from person to person.

But why might you gain weight just before your period? Well, there are a number of potential reasons. Ultimately, they all come down to the natural changes you experience in your body throughout your menstrual cycle.

Hormonal changes

Just before your period, your oestrogen levels drop rapidly, letting your body know that it’s time to start menstruation. However, progesterone levels rise after ovulation – and it’s this hormone shift that can cause your body to retain more water.¹

Importantly though, while this water retention might make the number on the scale increase or cause some swelling in puffiness in different areas of the body, this isn’t the same as gaining weight.^1,7

Period cravings

Ever wanted to eat a life-size bar of chocolate during your period? Or maybe a cheesy pizza?

Unfortunately, being on your period doesn’t tend to make you crave salad or vegetables.

Due to changes in your progesterone and metabolism, some emerging studies have shown that you’re more likely to crave salty and sweet food during this time.^8-11 However, eating salty foods and simple carbohydrates can lead to fluid retention and potentially result in extra water weight.¹²

Menstrual bloating

Your stomach might feel tight and swollen around five days before your period, causing pre-period weight gain.¹³

This may be due to hormonal changes, which can increase gas in your gastrointestinal tract and cause bloating, making you feel heavier.^13-15

Constipation

Just before your period starts, progesterone levels spike, which can lead to health problems in your digestive system.¹⁶

This can result in constipation before and during your period, meaning you might retain a little extra weight during this period that your body would normally get rid of.^16,17

A recent study involving 221 women in the Japanese population found that 58% of those with normal bowel movements had changes in their bowels due to menstruation. 19% of these changes in bowel movements were associated with constipation.¹⁷

Tips to help reduce period weight gain

Unfortunately, there’s no magic formula for preventing weight gain during your period.

However, there are a few things you could do to possibly reduce water retention and bloating. You should try to practise these healthy habits throughout the month, as this may help you to reduce weight gain and water retention during your period.

Lady in green top drinking a bottle of water in a park

Staying hydrated

Even though it might seem counterintuitive, making sure you drink plenty of water is our first piece of advice. This is because your body tends to conserve more fluid if you’re dehydrated.¹⁸

The NHS recommends drinking six to eight glasses of water each day.¹⁸So, make sure you keep a glass topped up on your desk so you can stay hydrated throughout the day.

Eat a balanced diet

To keep your digestive system running smoothly throughout your cycle it can be a good idea to eat plenty of whole, fibrous foods throughout the month.^19,20Taking probiotics to maintain healthy bacteria in your gut not only helps with bloating and constipation, but few studies suggest that they can also help balance hormonal health and potentially reduce menstrual pain.^21-24

To find out more about how to match up your diet with your cycle, visit our guide on what to eat during your menstrual cycle.

Exercise

When you’re suffering with cramps, working up a sweat in the gym might not be top of your to-do list.

However, sweating may help you get rid of that excess wate r that your body is holding on to.^25,26If you simply cannot face a low-to-moderate intensity workout, why not try a relaxing yoga session or going for a long walk instead?^27,28,29

Moving can also help with improving slower gut transit times (how quickly food moves through your body) caused by your hormonal changes.^30,31

Supplements

Some small studies have found that magnesium and vitamin B6 are effective in reducing PMS symptoms, including cravings and weight gain.^32,33However, there isn’t enough clinical evidence for this. What we do know however, is magnesium and vitamin B6 contributes to reducing those feelings of tiredness and fatigue you may experience during your period.

Two randomised, double-blind, placebo-controlled clinical trials showed the effectiveness of magnesium in relieving chronic constipation. One trial noted a 45% greater response rate in symptoms than the placebo group while the other noted a 68% overall improvement rate.^34,35,36

However, there isn’t any data to suggest whether magnesium can offer support for women who suffer from constipation/bloating in their menstrual cycle, and more research in this area is needed to confirm this.

When weight gain might not be a normal PMS symptom

It’s important to note, however, that if you’re experiencing weight gain in combination with irregular periods, then you could be suffering from an underlying issue like polycystic ovary syndrome (or PCOS).³⁷

But can PCOS cause weight gain? In short, yes.

This is because PCOS is a condition characterised by higher levels of androgens, such as testosterone, which can contribute to PCOS weight gain.^38,39

In PCOS, the body’s cells also become less responsive to insulin, causing the body to process carbohydrates less effectively and make extra insulin to compensate, leading to further weight gain.^38,40

The final say

Overall, weight gain caused by PMS is generally nothing to worry about.

However, if you’re looking to find a way to manage your symptoms of PMS, it can be a good idea to stay hydrated, eat well, move regularly, and try supplementing magnesium and vitamin B6.

Alternatively, if you’re concerned you may be struggling with PCOS, speak to a GP for more information.

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