Do you have a pair of special “fat pants” (I know, a terrible, terrible term) that you have to wear when you PMS every month? You’re not alone. I am most certainly a co-sufferer. As are millions of other women.

It’s challenging to link water weight to the menstrual cycle if you do any digging online. Unsuccessfully looking for a link drove me crazy for months. I really wanted to know, but couldn’t seem to find, a scientific explanation for why I gain a full notch on my belt, a pant size, and an inch of padding around my middle for several days at the end of each cycle.

I have also noticed that I gain the same inexplicable water weight whenever I am “dating” a person I really like (dating in airquotes because … well, you figure it out.). I know I sound crazy – but I really don’t think its too much of a leap to connect these two dots, either. Regular sex increases body processes like vaginal lubrication, hypothalamic productivity, and sex hormone production. Sex happens…some sort of hormone production goes up … and, it seems, Stefani gains weight. Fortunately I’ve learned to love my body enough that I haven’t given up sex in order to be skinny.



Is there a real, scientific link between estrogen, progesterone, and water weight?

Turns out there is.

Receptors for estrogens and progesterone are found in all sorts of tissues – not just the reproductive ones – such as the hypothalamus, the cardiovascular system, and the kidney. All three of these organs are intimately involved in the water retention process.

Via these receptors, estrogen and progesterone have the effect of:

-Regulating fluid intake

-Regulating sodium appetite

-Regulating renal (kidney) fluid

-Regulating sodium retention

In all female bodies. In healthy ones, the effects are minimal, but still present.

Both estrogen and progesterone do these things, and in somewhat opposite fashion.

Estrogen causes tissues to reabsorb sodium, which increases sodium levels in the body’s fluids. Elevated sodium causes water weight, because the body balances the extra sodium with extra water. The more sodium you have floating around in intercellular space, the more water your body is going to send to that space.

Estrogen makes sodium work like one of those little foam dinosaurs you get at the dollar store that expands to 60x its size once you put it in water.

EG, my waistline.

My waistline is a brontosaurus.


Progesterone, on the other hand, also causes sodium retention, but it doesn’t store it in the same free-floating space as estrogen it does. Instead, it stores it in certain “extracellular fluid compartments”  and also works to cause certain chemical changes to capillaries and other such things.  It also tends to work more on regulating other important hormones in this process, which down the line causes extra excretion of fluid rather than retention.  Thus, progesterone is somewhat of a diuretic. THIS IS SCIENCE SPEAK FOR ‘PROGESTERONE DOESN’T MAKE YOU RETAIN WATER WEIGHT; IT ELIMINATES IT.

IE – Progesterone is the straw in our dinosaur water glass.

dinosuars with straw

I am an artist.


Put simply – estrogen makes you retain water, and progesterone makes you dump it.

The Menstrual Cycle

A quick primer on the menstrual cycle is in order in order to understand how its related to water weight.

Day one of the menstrual cycle is the first day of bleeding. On day 1, estrogen and progesterone levels are both at their lowest. For the next two weeks–called the follicular phase–the body is in a fairly calm and neutral state. Estrogen and progesterone levels increase toward the end of the follicular phase, but not to drastically high levels.

At the end of these two weeks comes ovulation, which lasts about 36 hours.

After ovulation is the luteal phase, in which estrogen and progesterone levels gradually rise to very high levels, then fall for about a week preceding menstruation.

Then the cycle begins anew.




The fluctuating levels of estrogen and progesterone demonstrate why some women don’t experience PMS-related water weight, why some experience it at the middle of the luteal phase, why others experience it at the end, and why some have it the whole time.

As estrogen levels rise, the tendency to carry water also rises.

Progesterone is a counter-balance at this point, but sometimes it isn’t enough to balance the water weight, especially if you’re estrogen dominant.

Estrogen levels then begin to fall. This causes an eye in the calm of the storm – you may experience a decrease in water weight.

Yet the reason there is more storm to come is that, as progesterone levels are also falling, the body all of the sudden doesn’t have the same hormonal strength telling it to excrete water (this is the best theory so far, in my opinion, anyway.) It has become accustomed to higher progesterone levels, so as the progesterone levels fall off, the body loses some of its diuretic power, and water gets retained.

By day 1 or so of the next menstrual cycle most women’s bodies come back into water weight balance, as both estrogen and progesterone are low, and much better balanced than in the tumultuous times of the luteal phase.

 Other bodily effects? More important ones?!

It is worth noting, moreover, that the impact of estrogen and progesterone on body fluid is not limited to your pant size. It’s actually super important for your health!!!

Premenopausal women have long been notoriously known for experiencing lower incidence of cardiovascular disease than men. These differences tend to even out post-menopause. This has caused many researchers to theorize that estrogen and progesterone play a critical role in supporting cardiovascular health, as proper hydration and electrolyte balance are critical for blood pressure maintenance.

You don’t want to have excess estrogen and progesterone as a woman – but healthy levels help regulate blood pressure, and minimize the threat of cardiovascular stress.  The trick is to keep your dinosaurs robustly healthy, but not too big, and to have a healthfully functioning straw in your glass of water at all times.

So… what do I do?

The best ways to minimize the effects of water retention throughout your menstrual cycle are to:

-Be as healthy a weight as possible, which will reduce estrogen dominance

-Overcome estrogen dominance via these tips

-Be on a variety of birth control that is right for you and keeps your hormones in good balance

-Sleep well (Use blackout curtains, blue blockers, and natural bedding and sleepwear to keep pleasantly cool)

-Eat a paleo type diet! (Here’s one of my favorite resources on making the transition to paleo!)

-Eat lower carbohydrate – or lower starch, which tends to bloat a bit more than fruit does in terms of carbohydrate choice – at the times of the month you ordinarily bloat

-Monitor your salt intake and keep it on the low end during PMS (p.s. if you’re using regular table salt you are missing out!  This stuff is the BEST!)

-Drink plenty of fluids (Use BPA free bottles-I prefer glass ones like this– to help avoid estrogen dominance)

Love your body no matter some extra padding on its middle! Life is about so many important and beautiful things that are worthy of undivided attention.




And, of course, for more on being a woman and maintaining a healthy weight, JUST YOU WAIT for my kickass new weight loss book, Weight Loss Unlocked, which comes out on January 1!

In the meantime, grab a free chapter of the book @!

UPDATE: Weight Loss Unlocked is HERE! Yay!  Check it out now!

Do You Gain Weight When You PMS? Here's Why.

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