April 6, 2023/Women's Health

Yes, Weight Loss Can Impact Your Menstrual Cycle

If your period hasn’t come for three months, it’s best to see a doctor

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You’ve been killing it recently. You’re exercising harder — and longer — than ever before, and you officially fit in the dress. Your high school reunion is going to be legendary.

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There’s just one small problem: Aunt Flo’s giving you the silent treatment — your period is beyond late.

The technical term for a stopped period is “amenorrhea,” and it’s something you shouldn’t ignore.

We talked to endocrinologist Vinni Makin, MD, about one specific cause of amenorrhea: weight loss. If your period has stopped, it could be a sign that you’re exercising too much, eating too little or both.

Can weight loss impact your menstrual cycle?

The short answer: Yes, weight loss due to a restrictive diet, over-exercise — or a combination of the two — can absolutely cause you to lose your period.

The longer answer: Weight loss is contextual, and it’s important to keep in mind why somebody is losing weight before assuming it’s the reason their period stopped.

“When we are talking about weight loss,” says Dr. Makin, “if a person is trying to lose weight even though they are at a healthy weight already — maybe because of a body dysmorphic disorder — this can impact the menstrual cycle by making the periods irregular or by stopping the menstrual cycle altogether.”

What makes this topic complicated? Some people actually lose their period because they have overweight or obesity — and in some cases, polycystic ovary syndrome. For those individuals, losing even 5 to 10 pounds could restart their period. In other words, weight loss can cause period loss, but it can also make your cycle more regular, depending on your health.

Why does this happen?

Why would losing weight cause your period to go away?

“When you go through these kinds of physical changes, the body interprets it as stress,” Dr. Makin says.

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That stress, she explains, causes a fight-or-flight response. “Your body is conserving all its energy. It stops your menstrual cycle and reduces your hormone production because it only wants to use resources for things that are very, very, very important, like breathing and digesting.”

As you’ve probably already guessed, weight loss isn’t the only kind of stress that can cause that kind of physiological response. It can also happen in times of severe emotional stress. “We can even see it after surgery or a major illness,” Dr. Makin adds.

A diagnosis of exclusion

When healthcare providers are trying to figure out why you stopped getting a period, over-exercising and restrictive dieting are what are called “diagnoses of exclusion.” “It’s important that other disorders be ruled out first,” Dr. Makin explains.

The first and most important item on the diagnostic to-do list is making sure you aren’t pregnant. You should take a test to be sure. (The only exception is if you aren’t sexually active.)

Once you’ve confirmed you aren’t pregnant, it’s time to look for conditions that could be causing amenorrhea, like polycystic ovary syndrome, Cushing syndrome, and over- or underactive thyroid or celiac disease, to name a few. It may also be important to screen for testosterone-producing tumors, depending on when the symptoms started and their severity.

“There has to be a physical exam, medical history evaluation, lab work and maybe even some imaging done before we say ‘OK, there is no curable cause per se that we are looking at. This is being caused by lifestyle changes,’” Dr. Makin says.

Exercise

In the same way that not all weight loss causes you to lose your period, there’s no specific amount or kind of exercise that automatically translates to amenorrhea. Dr. Makin says there are a number of different physiological, psychological and environmental factors that impact your menstrual cycle.

What we do know is that menstrual dysfunction — like losing a period or bleeding without ovulating (an anovulatory cycle) — is fairly common.

A 2007 study found that it’s possible that up to 80% of women and people assigned female at birth (AFAB) who exercise vigorously may experience some form of menstrual dysfunction. Another study, this one conducted all the way back in 1983, found that women who run more than 50 miles a week are much more likely to experience amenorrhea.

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Busting amenorrhea myths

There are two common misconceptions about amenorrhea that have been circulating for a long time. First, losing your period is a sign that you’re physically fit. And second, losing your period means you have an eating disorder.

Myth #1: Not having your period means you’re more athletic than other people

It’s not uncommon to hear stories about elite athletes losing their periods. As a result, there’s a misconception that losing your period is a sign that you’re extremely physically fit.

The truth is actually the opposite.

Dr. Makin explains: “When somebody loses their period because of exercise or diet issues, that doesn’t mean they’re physically fit. That’s a sign that they are nutritionally deficient. They don’t have enough fat to support that hormone production.”

And she stresses: “Physical fitness is not defined by weight or by the amount or kind of exercise you do.”

Myth #2: If you stop getting your period, it’s because you have an eating disorder

There are many reasons why a person’s period might stop. Disordered eating is one explanation, but it’s only one of many.

Pregnancy, long-term stress, injury and chronic illness are just a few of the many reasons people lose their periods. Amenorrhea is also a symptom of several medical conditions like fragile X syndrome or cystic fibrosis.

It’s also possible to have a disordered relationship with food that doesn’t cause amenorrhea. Having your period is not, in and of itself, a definitive sign of whether you’re getting the nourishment your body needs.

Can you get your period back?

Losing your period can be scary, especially if you’re planning to become pregnant in the future. But can you get it back once you’ve lost it? The answer is yes, with one caveat: You have to make some significant adjustments to your lifestyle.

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“You need to both decrease exercise and increase your caloric intake,” Dr. Makin states. As a rule of thumb, you should be striving to return to the weight you were when your cycle was arriving every month at the expected time. In some cases, people actually have to gain more weight to get their period restarted.

These changes aren’t easy to make, especially if you’re struggling with issues like body dysmorphia. That’s why it’s important to work with a healthcare provider. They can help you determine the healthiest and safest way to get you to your goal weight and get you the resources you need to overcome the obstacles in your way.

“People can often be reluctant to change their lifestyle and might need the help of a team of specialists, like a psychologist, primary care physician or a pediatrician, a dietitian and an exercise physiologist,” Dr. Makin notes.

How fast you get your period back after losing it, then, isn’t a simple calculation. “It depends on the kind of health program you’re following and how fast you’re making lifestyle changes,” she says.

Can you get your period back without changing your lifestyle?

When it comes to amenorrhea, not all periods are created equal.

“Technically, you can induce a period by going on birth control pills or using estrogen patches and progesterone pills,” Dr. Makin explains, “but that does not negate the adverse effects you will get from an absent period. It won’t restart your ovulation. For people who are trying to conceive, it’s not going to help with that.”

In other words, you can’t restart your period in a way that’s healthy and natural without gaining weight and changing your exercise routine.

When should you be concerned?

When you should be concerned depends on who you are and the circumstances surrounding your period loss.

“If you’re sexually active, the first thing you need to do is check for pregnancy, even if you don’t think you could be pregnant.” Dr. Makin advises. “Even women who have irregular periods might be ovulating. So, you can’t assume you cannot get pregnant. You can get pregnant.”

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If you’re under the age of 45 and haven’t had a period for three months — and you’ve confirmed that you aren’t pregnant — you need to see a doctor, regardless of whether or not your weight, diet or exercise regime has recently changed.

If you’re over 45, you may be experiencing perimenopause. It may still be a good idea to talk to a healthcare provider, just to be sure you know what’s happening with your body, and for advice on managing any symptoms you may be experiencing.

It’s also important to remember that it can take one to two years after menarche (your first period) to achieve a regular cycle. That doesn’t mean you should ignore a missing period. It does mean that some irregularity is to be expected. Your doctor may suggest going on medication or making lifestyle changes to help stabilize your cycle.

The bottom line

Some women and people assigned female at birth (AFAB) may be less-than-pumped about getting their period, and that’s understandable. It can be inconvenient and, in some cases, downright just not fun. Whether you’re trying to become pregnant or just want to have one vacation where you aren’t worried about your tampon supply, you’ve probably wished your period away at least once. But if it disappears without explanation? Well, that’s a red (or not-so-red) flag.

If you’ve stopped getting your period or it’s become irregular, the first thing you need to do — if you’re sexually active — is take a pregnancy test, regardless of how long it’s been since you bled last.

The next thing you need to do is see a doctor. Missing a period for more than three months is a health concern regardless of your weight or fitness level. You can get your period back, but if you lost it because of over-exercise or restrictive eating practices, it won’t come back until you address your nutritional deficiency.

Remember: Your weight and athleticism don’t define you. And they shouldn’t take priority over your health and well-being. The best you is a healthy you.

Learn more about our editorial process.

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