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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As a physician for adolescent girls and young women (and as an 80s girl who grew up feeling all the pressure to be thin) eating disorders have always been on my radar. They are common, serious, and tricky to recognize and treat. Over the years, I’ve been involved in the diagnosis and treatment of many anorexic girls. I’m as confident as physician can be in understanding the risk factors, prevention strategies, warning signs, and diagnosis. 

So when I ended up with 3 daughters, I was pretty sure anorexia was one health condition my girls would not have to deal with. I raised them with body positivity and confidence-growing experiences. I fed them mostly-healthy-but-not-restrictive nutrition. They had open-access to ice cream and other treats in the house. I wasn’t worried. 

Until I realized that my daughter was anorexic.

In retrospect, there were some vague warning signs. I noticed weight loss, but she had been sick, recently diagnosed with Celiac disease which meant she had to remove all gluten (bread and pasta – her favorites) from her diet. Her friends and their mothers noticed her weight loss and, like so many women and girls, kept telling her how great she looked. 

We talked openly about getting enough nutrition as we learned the ins and outs of her new gluten-free diet. She assured me she was fine, but some of her behaviors were beginning to change. She was keeping her room immaculate. She was unusually quiet — or explosive. When she sat at the kitchen table, she kept her legs bouncing in constant motion. I remember noticing her boney spine at the kitchen counter one day, but then telling myself in total denial, “Nah, it can’t be…she’s just been sick. She’s not the anorexic type. She’s always been so confident and happy.” But instinctively, there was doubt and worry. I found myself in a sideways glance, eyes squinting as I questioned my own internal voice. It finally struck me. My daughter was anorexic. 

How did I let this happen? I felt like an idiot. I felt like a horrible mother. I questioned my clinical skills. 

Without detailing two of the most difficult years of my life, let me tell you a few personal insights I gained during her recovery (and my therapy) and since then:

• It can happen to anyone in any family. 
• It is not caused by a parenting failure. 
• Early recognition and aggressive treatment are critical to recovery.
• Treatment is hard.
• Families do hard things.
• Full recovery is possible.

In the time since we faced this in our family, more research has improved what we understand about anorexia and other eating disorders.

Here are some facts you should know about anorexia (we also offer an on-demand video class, Understanding Anorexia, HERE):

👉🏼 The causes are complex and a combination of genetics, her environment, and weight loss triggers. Check out this video tip for details on the risk factors. 

👉🏾 It is a brain-based illness that can have lasting effects on physical growth, brain function, and mental health. 

👉🏽 There is no stereotype to identify those who will develop anorexia – all genders, sizes, shapes, races are susceptible, but most of the time, it starts in childhood or early adolescence (and currently, it’s starting at younger ages than ever before).

👉🏼 She does not need to believe she is fat or have a distorted body image to have anorexia.

👉🏾 Over ⅓ of kids diagnosed with anorexia today are overweight or obese, but their diagnosis is often delayed because our society is fat-phobic and thinks weight loss is always good for overweight kids – no matter how they lose the weight. 

👉🏽 Early recognition and treatment increase the possibility of full recovery.

👉🏼 The primary treatment is food, not medications. 

👉🏾 The anorexic patient’s brain is not functioning normally because of malnutrition. We are learning more and more about the importance of nutrition in the way the brain develops and functions. The brain cannot recover (including emotions, decision making, insight) until it is fed appropriately. Until she recovers, she cannot make rational decisions that involve eating habits or food.

👉🏽 The most effective treatments are family-based and occur within the home (not in a hospital). Therapists and nutritionists experienced in treating eating disorders provide guidance and support, but the family does most of the work. 

👉🏼 If anorexia affects your family or a friends’ family, there should be no shame or embarrassment. This disease is no different than any other for which we eagerly offer empathy and support. 

👉🏾 If you have concerns about anorexia and your child, please speak with her doctor as soon as possible!