The Science Behind Weight Gain During Your Period | Signos

Learn about the hormonal and physiological reasons you gain weight during your period, plus expert tips and strategies for prevention.

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by
Caitlin Beale, MS, RDN
— Signos
Health & Nutrition Writer
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Updated by

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Science-based and reviewed

Published:
May 17, 2024
August 14, 2023
— Updated:
August 15, 2023

Table of Contents

That feeling when your clothes feel a little snug around the waistline, so you check your calendar and—surprise!—your period is due in a few days. Cramps and bloating accompanied by mood swings, fatigue, and appetite changes are common symptoms and universally dreaded by anyone with a menstrual cycle.

Weight gain during periods is normal, and most of the time, it isn't the kind of weight that stays on your body. Instead, it's usually a combination of water retention and hormonal fluctuations contributing to feeling bloated and puffy, but that doesn't make it any less uncomfortable.

Let's take a closer look at why this happens and how you can minimize the effect of period weight gain.

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Is Gaining Weight During Your Period Normal?

Gaining weight during your period is normal. Although women and midwives have known and experienced it for centuries, the scientific community became interested in understanding the weight fluctuations associated with the menstrual cycle in the early 1900s, calling it "menstrual edema" (edema is the medical term for swelling from fluid).  

Body weight doesn't just shift during your period, it can change throughout the month and even the day based on factors like sleep, exercise, stress levels, and diet. Period weight gain may show up as extra pounds on the scale, or it may feel like your clothes fit differently than the day before. It's not fun but also not unusual.

How Much Weight Do You Gain During Your Period?

There isn't a lot of research on the amount of weight women gain during their period, but two to five pounds is the average. Everyone is different, but weight gain above five pounds may mean checking in with your doctor is a good idea.

What Are the Top Causes of Period Weight Gain?

Reasons for weight during your period can vary, but hormonal shifts throughout the month are usually the underlying cause.

Hormones follow a general pattern each month, rising and falling to trigger processes like ovulation (when an egg is released for fertilization) and a menstrual period when fertilization doesn't occur. Hormones also affect mood, appetite, energy levels, and so much more; it's no wonder they also influence weight.

Most of the top causes of period weight gain are associated with hormonal changes. Let's take a closer look at each.

Hormonal Changes

Estrogen and progesterone are sex hormones that may influence weight gain during your period. In a typical cycle, estrogen, the hormone responsible for regulating the menstrual cycle (among many other jobs), peaks twice: once before ovulation and again before your period starts.

Meanwhile, progesterone levels stay relatively consistent until it rises and peaks during the second half of your cycle. Both estrogen and progesterone drop dramatically at the end of the cycle, which triggers your period.

Sensitivity to the rise and fall of progesterone and estrogen is hypothesized to be the cause of PMS symptoms like bloating and water retention.3  While it may feel like you've gained weight, it's likely just excess fluid that normalizes once hormone levels rise again.

Food Cravings or Overeating

We may joke about chocolate cravings and menstruation, but there's some science behind it. Serotonin, a neurotransmitter responsible for regulating mood and appetite, decreases when estrogen levels drop. This drop can increase cravings for carbohydrates, which may boost serotonin production. Our bodies may instinctively crave carbs to increase serotonin levels and improve mood. 

Progesterone also can increase your appetite in the days leading up to your period, which explains why some people tend to crave things more right before than actually during menstruation.  In reality, it's unlikely that you will eat enough to gain five pounds, but you may retain extra water weight or just feel uncomfortable after eating extra sweets or salty foods.

Bloating and Constipation

Gastrointestinal (GI) symptoms like bloating and constipation are also incredibly common. While they don't cause direct weight gain, they can make you feel heavy and uncomfortable.

Once again, changes in progesterone may be the culprit, as the hormone can slow down gastric transit time, making it harder to have a bowel movement in the days leading up to your period. Constipation can add to bloating and cause gas and abdominal discomfort. Once menstruation begins, the opposite may be true, as inflammatory prostaglandins can lead to increased uterine contractions that cause cramps and more frequent bowel movements.

Low Magnesium

Magnesium is a mineral that helps to regulate water balance in the body and is essential for proper muscle function and bone health. It also plays a role in blood sugar balance, which helps to stabilize hunger levels and food cravings. 

Low magnesium levels may contribute to low energy, muscle cramps, mood swings, and water retention. Some research suggests that low magnesium levels can contribute to PMS symptoms, including bloating and water retention.

Skipping the Gym

Skipping a workout here and there isn't a big deal, and sometimes it's better to take a rest day when you're feeling run down. But if you aren't moving your body for a week, it may make you feel even worse. Throwing on your spandex may not feel like the most appealing thing in the world when you're on your period, but physical activity can help relieve symptoms associated with PMS.

Fluid Retention

Once again, you can thank hormones for your period water weight.3 Progesterone can affect the balance of other hormones involved in fluid regulation, such as aldosterone and vasopressin. These hormones influence sodium and water reabsorption in the kidneys, potentially leading to fluid retention.

How Long Can Period Weight Gain Last?

Since much of the weight associated with periods is not actual weight gain but water retention, it should dissipate after the menstrual cycle, and hormones begin to rise again. If bloating or heaviness continues, or you gain a significant amount of weight outside your normal range, you consider visiting your OB-GYN or primary care doctor to discuss it.

How to Treat and Prevent Period Weight Gain and Bloating

Preventing period weight gain and bloating can be easy for some people, and it may seem like an uphill battle for others. The first step first to recognize that it's completely normal to experience some degree of fluctuations in your weight during the menstrual cycle, and it doesn't mean you are doing anything wrong. But there are steps you can take to help you feel better in your body throughout the month that can support a healthy approach to your cycle.

Choose High-Fiber Foods

High-fiber foods like produce, whole grains, legumes, nuts, and seeds can help you stay regular and support healthy hormone levels. Fiber is also helpful for blood sugar balance and cravings, so you are less likely to reach for unhealthy snacks when you feel tired or bloated.

Tip: Add more fiber to your diet by snacking on nuts and seeds, adding beans as a side dish or topping for salads, and choosing whole grains like quinoa and sprouted whole wheat bread.

Stay Hydrated

It sounds counterintuitive if you feel like you're retaining water, but optimal hydration can help you flush out the excess salt that may be contributing to bloating. Eight glasses a day is the general recommendation, but individual needs may vary depending on your activity level and body size. A good rule of thumb is to check out your urine: clear or light yellow means you're well-hydrated.

Tip: Carry around a water bottle and set reminders to drink throughout the day on your phone.

Move and Exercise

Again, movement and exercise may feel like the last thing you want to do if you aren't feeling well, but they can be helpful for both bloating and fatigue. You don't need to run miles or jump into a high-impact class; yoga, walking, or swimming are great choices. Anything that gets your heart pumping and your body moving can help with water retention and boost your mood. Plus, regular exercise is linked to a lower incidence of PMS.  

Tip: Make a playlist or find a podcast you love and go on a no-pressure walk to get your body moving. 

Supplement with Magnesium

Magnesium may help reduce water retention, bloating, constipation, breast tenderness, and mood swings. Magnesium's ability to relax smooth muscles may also help ease menstrual cramps.13 It also aids neurotransmitter regulation, potentially improving mood and reducing anxiety and irritability associated with PMS. 

Tip: Check with a healthcare professional to determine the appropriate dosage and type of magnesium to meet your needs. You can also incorporate magnesium-rich foods like leafy green vegetables, nuts, seeds, legumes, and whole grains. 

Bump Up Vitamin B6

Vitamin B6 is often used to support PMS symptoms such as bloating, breast tenderness, and irritability. Research suggests that vitamin B6 helps to reduce the intensity of premenstrual symptoms and improves general well-being, especially when combined with magnesium.  

Tip: Vitamin B6 can be found in meat, fish, eggs, legumes, nuts, seeds, and bananas or as a dietary supplement. 

Reduce Salt Intake

While sodium is essential for bodily functions, excessive consumption can lead to fluid retention. When sodium levels are elevated, your body retains more water to dilute the excess sodium concentration. This, in combination with progesterone's effect on fluid retention, can cause an uncomfortable bloating sensation and weight gain for some women.

Tip: Salt sneaks into our diets in many ways, from processed foods and restaurant meals to condiments like soy sauce. Try reducing your intake of processed or pre-packaged foods, check labels, and experiment with herbs and spices instead of extra salt.

Keep Tabs On Sugar Intake

Weight gain from water weight may be temporary, but weight gain caused by consuming too many calories may not go away quickly. Sugary snacks like candy, soda, and baked goods spike your blood sugar and add extra calories to your diet, contributing to weight gain.

Tip: Don't completely deprive yourself of all treats, as it can lead to even more cravings or food binges. If you crave a treat, eat a mindful amount, enjoy it, and move on. The more you tell yourself you can't have something, the more likely you'll indulge in excess.

Visit Your OB-GYN

If you feel like you've tried everything and are still concerned about your weight gain or the bloating you experience during your period, it's best to talk to a doctor. A visit to your gynecologist can help determine if an underlying hormonal condition is causing symptoms and find a personalized solution. Women often incorrectly believe they just have to deal with symptoms like weight gain or pain, but talking to a trusted doctor can help find the right support for you. 

Tip: If your OB-GYN recommends hormone therapy or medication to ease menstrual symptoms, ensure you understand all the possible side effects and discuss any concerns with your healthcare provider before beginning treatment. 

Learn How To Manage Weight Throughout Your Cycle with Signos' Expert Advice

Lifestyle changes are often the best way to prevent and reduce period weight gain and bloating. Cultivating better habits can help you stay healthy and balanced at that time of the month and throughout your cycle.

Signos can make it easier to make changes that will leave you feeling confident in your body and empowered in self-care. From educating yourself about the foods that provide lasting energy and stable blood sugar to how your body responds to stress and exercise, Signos gives you real-time feedback for whole-body health

Just getting started in your journey? You can learn more about nutrition and healthy habits on Signos' blog or find out if Signos is a good fit for you by taking a quick quiz here.

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About the author

Caitlin Beale is a registered dietitian and nutrition writer with a master’s degree in nutrition. She has a background in acute care, integrative wellness, and clinical nutrition.

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