One afternoon when I was driving carpool, my daughter’s friend was telling us about how much she enjoys running cross country. She listed several things that make it her favorite sport—being outside in nature, running with friends, getting exercise—but one of those things was “and I don’t have my period during cross country season. It’s great!“

To which the other three girls in the car reacted with jealous comments that they might join cross country for that!

As an ob-gyn, I wanted nothing more than a giant red flag to wave around that car. I knew I had to chat with her mom and the cross country coach—and ultimately the entire team—about something called RED-S.

Here’s why.

Her Period Is Actually a Vital Sign

I get it. Periods can be inconvenient, messy, and sometimes uncomfortable. But it’s really important to understand that having a regular menstrual cycle is actually one of the best indicators that her body has enough energy to do all the amazing things it needs to do—including building strong bones, maintaining a strong immune system, and yes, performing well in sports.

When her period stops or becomes irregular during intense training, it’s not a perk. It’s her body waving a red flag that says, “Hey! I don’t have enough fuel to keep everything running!“

What Is RED-S?

RED-S stands for Relative Energy Deficiency in Sport. It’s what happens when athletes don’t eat enough calories to support both their training AND all the other things their bodies need energy for—like growing, thinking, healing, and having periods.

Think of it this way: The body is like a phone. If it’s constantly being used all day but only charged to 20%, eventually it’s going to shut down some functions to conserve battery. The body does the same thing when it doesn’t get enough “charge” (fuel in the form of calories). It starts shutting down things it considers “non-essential”—and unfortunately, the reproductive system is one of the first to be affected.

The Three Big Problems

When we first started recognizing this pattern in female athletes, we called it the “Female Athlete Triad” because it involved three interconnected problems:

1. Not eating enough for activity level – Sometimes this is intentional (trying to stay lean for a sport), and sometimes it’s unintentional (just not realizing how much fuel she actually needs). Most active teen girls need at least 2,000-2,400 calories per day, and athletes need even more. 
2. Missing or irregular periods – When the body doesn’t have enough energy, it saves energy by shutting down the hormones that control the menstrual cycle. 
3. Weak bones – Those same hormones (especially estrogen) are also what help build strong bones. When estrogen levels are low and periods stop, girls are not building bone density during the exact years when they’re supposed to be. This means stress fractures now and possibly osteoporosis as early as young adulthood. 

The Red Flags

How do you know if your daughter or someone you care about might have RED-S? Look for these warning signs:

• Missing periods or very irregular cycles
• Frequent injuries, especially stress fractures
• Always feeling tired or run-down
• Performance getting worse instead of better
• Getting sick a lot
• Overly focused on food, weight, or body composition

What to Do About It

The good news? RED-S is treatable. The main goal is to restore energy balance:

Increase calories. She might need to add 300-600 calories per day, with a focus on protein and carbohydrates. Working with a sports nutritionist is really helpful.

Possibly reduce training. Sometimes athletes need to dial back training by 10-20% temporarily to let the body recover.

Build bone health. Ensure she’s getting enough calcium (1,200 mg daily) and vitamin D (1,280-2,000 IU daily) through food and supplements.

Get her period back naturally. Once energy balance is restored, her period should return on its own within a few months. That’s how you know she’s getting better. (And no, birth control pills don’t fix this—they just mask the problem.)

Work with a team. The best treatment involves her doctor, a sports nutritionist, possibly a mental health counselor, her coach, and you—all working together.

Back to That Carpool Conversation

After that carpool ride, I did reach out to my daughter’s friend’s mom. We had a good conversation, and together we connected with the coach. The result? The whole cross country team got education about RED-S, several girls got evaluated by their doctors, and the team culture shifted to emphasize healthy fueling.

That runner? She’s doing great now, with regular periods and no stress fractures. And she still loves cross country—maybe even more, because now she has the energy to truly enjoy it.

If your daughter is an athlete who’s missing periods, please don’t brush it off. Her period isn’t just an inconvenience—it’s a vital sign. And when it goes missing, her body is trying to tell you something important.

Listen to it. Her future self will thank you.

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 We know our Girlology community has moms with girls of all ages, and questions about birth control may not be on your radar. But whether you have a current or future teen, some essential facts can prepare you as you and your girl head toward adolescence where you’re both sure to encounter LOTS of MYTHS. 

For many teens, some form of birth control will be used to treat or help manage health issues such as menstrual migraines, acne, anemia, painful periods, endometriosis, ovarian cysts, bleeding disorders and other complex medical conditions. Some teens will need pregnancy prevention. And sometimes, a girl just wants to make her periods less disruptive for reasons that might be related to athletic performance, an upcoming vacation, or just because. 

When it comes to all the reasons a teen might need some help with hormones, the most common choice is birth control pills. Sure, there are other methods that may be more reliable like the shot, IUD or implant, but in this piece, I’m focusing on “the pill” which contains both estrogen and progesterone (not to be confused with the “mini-pill which contains ONLY progesterone, is less effective for teens, and was recently approved for over the counter sales without a prescription). 

In medicine, “the pill” is also referred to as oral contraceptive pills (ocp) or Combined Hormonal Contraceptives (a grouping that also includes the birth control patch and vaginal contraceptive ring which are both as effective as the pill and are used for many of the same reasons – the hormones are just absorbed through the skin or the vaginal walls)

So let me get to the 5 most common myths we hear from patients in the office. The facts I present are based on decades of medical research. I hope this helps you and your daughter make decisions that are grounded in reality – not myths or unfounded claims from self-appointed birth control experts on tik tok who are trying to sell supplements, wellness coaching, or some other unproven cure. If you want a deeper discussion on birth control safety and research, watch this video: Is It OK for Her to Take Birth Control Pills?

Myth 1

❌ Birth control pills cause weight gain.

Lots and lots of studies have looked at weight and birth control methods and the bottom line is – birth control pills are weight neutral. They don’t cause weight gain. They don’t cause weight loss. However, teens are naturally and normally supposed to gain body fat as they mature into young adulthood, so they WILL gain weight as they develop. AND, as teens become more independent, changes in their eating habits and activity levels are the other cause for significant weight gain. Only one birth control method has consistently shown weight gain, especially among teens who are already overweight – that is Depo-Provera or the birth control shot.

Myth 2

❌ Birth control pills increase her risk for breast cancer.

Teens who take birth control pills do not have an increased lifetime risk of breast cancer. This includes teens with a family history of breast cancer and even the BRCA genetic mutation for breast cancer risk. BUT, birth control pills have been proven to REDUCE the risk for ovarian cancer, endometrial cancer, and colon cancer.

Myth 3

❌ Birth control pills cause depression.

Ok. Bear with me on this one. Depression and other mood disorders are especially common among adolescent girls, and lots of adolescent girls take birth control pills. So there are some challenges to getting a clear answer regarding whether the pill contributes to depression or depression shows up and she just happens to also be on it. Either way, it’s important to look for an answer – and LOTS of researchers have tried. Unfortunately, numerous studies have found no clear link. However, one fairly recent, well-designed study out of Denmark got a lot of media attention when it showed an association (not a cause) between all hormonal birth control methods and depression; and the link was more significant among teens.

Interestingly, in that study, the biggest risk of depression occurred with progesterone-only contraceptives (which include the IUD, implant, shot, and mini-pill) but it was less with traditional birth control pills (which contain estrogen and progesterone). Also, the increase in depression was SLIGHT. 

For women not on birth control, the baseline rate of depression was 1.7 per 1000 people. For those using birth control, the depression rate was 2.3 per 1000. The difference was statistically significant, but in real life, that’s a very small increase. And that’s the best data we have after decades of looking at this issue.

The bottom line is that every individual can respond differently to medications, so it’s always important to pay attention to side effects or any concerns after starting a new prescription, including birth control pills. It is still accurate to share that the risk of pills causing or worsening depression is very very small, but if it happens to you, we want to know because we can try another formulation of pill or another method!

Myth 4

❌ Teens should be placed on the lowest dose birth control pills.

This is another myth that many moms find surprising. First, understand that almost ALL ocps prescribed today are by definition “low dose,” which means the amount of estrogen (ethinyl estradiol) is 35 mcg or less, but “low doses” range from 10 – 35 mcg.

Secondly, adolescence is the most important time in a female’s life for building bone density. Although estrogen is known to strengthen bones, and birth control pills contain estrogen – all doses do not have the same effect. For teens, optimal bone density development doesn’t happen when the pill has doses of the estrogen that are lower than 30 mcg. That means the ultra low dose 10 mcg pills and even the commonly prescribed 20 mcg doses may be harmful to her bone development.

Besides bones, the lower doses of ocps tend to have more breakthrough bleeding (spotting) and are not always the best at controlling pain and heavy bleeding – all things that make her stop her pills. 

For these reasons, most contraceptive experts treating adolescents recommend birth control pills with 30-35 mcg of the estrogen component. 

Myth 5

❌ Birth control pills make it harder to get pregnant in the future.

False. The reality is that taking birth control pills during the reproductive years has been shown to be slightly protective of future fertility and definitely does not harm or reduce someone’s ability to get pregnant once they are off the pill. This fact is related to the rates of pelvic inflammatory disease (a sexually transmitted infection that spreads into the uterus and fallopian tubes), which are lower among women on the pill than those not on hormonal birth control. 

 

For teens, there are very few contraindications for using hormonal birth control, and the most important thing to know is that any form of birth control (pills, patch, ring, shot, IUD, implant) is safer than pregnancy – always. 

One more thing – 

There are over 150 brands and generic formulations of birth control pills on the market in the U.S. and there are not many physicians who understand the differences between the formulations. However, the majority of teens who start birth control pills will do fine with the one they are given. Those who don’t respond or have significant side effects will usually do better with a different formulation that is wisely selected based on her symptoms. There is no doubt, however, that some people just don’t tolerate or like birth control pills.

For more on birth control and teens, check out the following short tips for Girlology members:

Understanding Side Effects of Birth Control Pills

How to Manage Period Problems with Birth Control Pills 

 

Did you know Girlology has grade-by-grade playlists listing on-demand video and downloadable content to support her and you through the entire journey? Learn More 

With warmer weather and Spring Breaking, it seems that many of you are thinking about (and stressed about) your daughters’ bathing suits. We get dozens of questions on this topic every year, and the range of questions is as varied as the range of very strong opinions about what is and isn’t ok for girls to wear.

Some of the questions we’ve received recently sum up the recurring themes in the great bathing suit quandaries. I’ve provided some simple, body-positive suggestions that may help (or may not — this is definitely a highly complex and nuanced topic). Let us know how you’re handling these challenges in your home!

 

She’s hiding her body

“My daughter only wears baggy clothes and insists on a full-cover, black one-piece. Her figure is so cute. How can I help her feel more comfortable with it?”

If she likes baggy clothes and wants a full-coverage bathing suit – great. There’s no need to push her into something more form fitting. It’s particularly common for some girls to want to stay covered when they become aware of their morphing body and aren’t quite ready to show others what’s been going on under those giant T-shirts. It doesn’t necessarily mean she has a body image problem, it may just be a time of adjustment. 

You don’t need to know the reason, just start looking for those black one-piece suits. If you have the means, give her a few options and let her choose one she likes best. Remember that you can’t talk her into loving her body, but you can influence her body acceptance by modeling your own and staying focused on the awesome things her body does instead of how it looks. Also – one last suggestion: telling her that her body is cute won’t help, and can actually hurt by perpetuating our societal knee-jerk that focuses on looks instead of other more important traits.

 

Her suit is too small

“My daughter put on last year’s bathing suit, and yikes. We need something bigger! How do I tell her without making her self-conscious?”

When our kids grow, it’s normally seen as an exciting event and sign of health, but when girls’ bodies grow in new places during adolescence, why does everyone act so surprised? If you’re worried about telling her, don’t be. She already knows she’s growing. But the way you talk with her about it can change everything. If you can avoid this scenario before she even tries on last year’s suit, do it. Suggest a shopping trip (or order) anticipating that normal growth means a new swimsuit. If she’s standing in front of you spilling out of last year’s suit, stay calm, matter of fact, and leave the ball in her court, “Looks like it could be time for a new suit. What style do you think you want this year?” 

A girl in a woman’s body

“This year, My 12 year old’s body would definitely fit in a women’s size suit, but she still loves to run around and play. Where do we shop for something comfortable and appropriate?”

Thankfully, this solution is more practical and less emotional. Even though she might be perfectly proportioned for the teen suits, skip the teen department and go straight to the women’s department or sporting good stores where there’s a larger variety of options, including tankinis, one-pieces, and even boy-shorts, board shorts, and rash guard tops that also double as great sun-protection. If you’ll be shopping virtually there are some great options at some of the traditional catalog stores like LL Bean and Land’s End. If she still loves to run around and play, she deserves a suit that lets her do that without wedgies or nip slips!

 

I’m worried she’ll be teased

“My 13 year old daughter is asking for a bikini, but she really doesn’t have the body for it. I want to encourage her body acceptance, but I’m worried that at her age, she will be teased or bullied. What should I do?

This is where parenting tween and teen girls can become excruciatingly challenging. Is our “protection” nothing more than body shaming and judgment? 

My first instinct is to say that the most beautiful bikini body is a happy and confident body – and I believe that with all my heart. But I think we owe our daughters more than “you’re beautiful.” 

At 13, girls are very capable of understanding that as parents, we can feel conflicted about what we want and don’t want for our children. They are also capable of reflecting on choices they make. 

So tell her what you love (her confidence, her style). Tell her what worries you (some people judge others for stupid reasons; some people may sexualize her body and make her feel uncomfortable; she may feel restricted and less free to move around without tugging on her suit). Then get curious without expressing judgment or emotion. Why does she want a bikini? Is there another style she might like to have as well? 

Obviously there’s a delicate balance between helping your daughter feel empowered and helping prepare her for the reality that people can be jerks. You’ve probably said “life’s not fair” before, and this is one more example and a conversation that you’ll need to have again and again as she grows. 

Just make sure she knows that you are her biggest fan no matter what she decides to wear – and if that’s a bikini, then good for her! She is already winning in the body confidence arena.

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This is a kind and very wise community, so if you are having other dilemmas like these, feel free to ask for help in the comments section. We’re here to help each other as we all parent through puberty! 

If you want to keep it in a more private space, our members have access to our private online forum where you can ask anything and get responses from our physicians, mental health experts, and other caring adults. Maybe it’s a great time to join!

Did you know Girlology has grade-by-grade video on demand playlists to support her and you through all things puberty and adolescence. Our doctor-moms cover topics like this and lots others! Learn More about joining HERE.