Is It Low Energy Availability/Relative Energy Deficiency in Sport, Lactation, or Perimenopause Contributing to Your Symptoms?

Fatigue.

Interrupted sleep.

Mood changes.

Body composition changes.

Reduced performance and recovery.

Irregular or absent periods.

If you’re an active woman, you’ve likely felt some (or all) of these at some point. But here’s the problem: these symptoms can show up in completely different life phases — from your 20s to your 40s and beyond, and yet, they’re often dismissed or mislabelled.

Is it Relative Energy Deficiency in Sport (REDs) ? Perimenopause? The postpartum phase? Or all three at once?!

Truthfully, this post won’t give you a definitive answer, because there’s no single test that can. But it can help you reflect on your current eating and training practices, and how they may be shaping your hormonal profile and symptoms.

Why It’s So Confusing

While healthcare providers play an essential role in screening and diagnosis, many athletes fall through the cracks. OBGYNs are experts in reproductive health, not sports physiology. Primary care providers rarely have the time (or tools) to assess energy intake and training load. Endocrinologists understand eating disorders, but REDS doesn’t always present that way. And not every athlete even has access to sports medicine or consistent primary care, especially in rural communities or at the recreational level.

Without a nutrition assessment, it’s nearly impossible to pinpoint the cause. Hormones don’t exist in isolation — they respond to how you fuel, train, sleep, and recover. Getting clarity starts with understanding your energy balance, not chasing another supplement.

When “She’s Just Fit” Isn’t the Whole Story

We’ve all heard it before: “She’s just fit.”

Or worse, I once saw an athlete in her mid-20s who’d had an expensive, non–evidence-based DUTCH test (red flag) with a non-sport practitioner, and was told she was in perimenopause.

Meanwhile, a full nutrition assessment revealed prolonged low energy availability, low carbohydrate availability, insufficient essential body fat (despite a normal BMI), a history of bone stress injuries, and primary amenorrhea.

Can you imagine if she had Googled “what to eat for perimenopause” instead of getting help from a sport dietitian? EEEK.

Where Age Bias Shows Up

Age bias adds another layer. When athletes in their 40s present with fatigue, irregular cycles, or slower recovery, it’s often chalked up to “just aging” or perimenopause — and REDS isn’t even on the radar! The same symptoms that would trigger a full workup in a 25-year-old are too often dismissed in a 45-year-old as “normal.”

Why a Sport Nutrition Assessment Matters

This is where a sports dietitian becomes essential. A comprehensive assessment considers:

• Energy balance

• Carbohydrate availability

• Macronutrient balance with daily training load

• Nutrient status

• Recovery

• Relationship with food, body and exercise

All of these influence how your body performs and adapts. Without this lens, it’s easy to mistake a nutritional problem for a hormonal inevitability, and to miss the real solution altogether.

Let’s Start with the Overlap

Low Energy Availability (LEA) and Relative Energy Deficiency in Sport (REDs), lactation, and perimenopause can all present with:

• Fatigue and low mood

• Poor sleep

• Decreased strength or performance

• Changes in recovery or body composition

• Disrupted menstrual cycles

• Reduced fertility

• Reduced bone health, temporary or permanent

The catch?

Each of these conditions occurs for very different reasons and affects different populations. But because the symptoms can look so similar, it’s easy to miss what’s actually going on.

1️⃣ Low Energy Availability (LEA) / REDs

Population:

Active individuals of any gender and age, with highest risk in endurance, aesthetic, or weight-class sports.

Mechanism:

When calorie intake doesn’t meet the demands of exercise plus basic physiological function, the body begins to conserve energy. Reproductive hormones like estrogen and progesterone drop, thyroid function slows, and cortisol often rises. This suppression affects multiple systems, including metabolism, reproduction, and bone health.

Clinical Picture:

• Menstrual irregularities or loss of period

• Fatigue, low libido, poor recovery

• Recurrent illness or bone stress injuries

• GI symptoms and cold intolerance

• Low mood, irritability, or anxiety

Key Hormones Affected:

Reduced gonadotropin-releasing hormone (GnRH) leads to lower LH and FSH, which decreases estrogen and testosterone, impairing reproductive function, bone formation, and muscle protein synthesis.

Lower T3  (thyroid hormone) slows metabolism and thermogenesis.

Cortisol tends to rise, increasing stress hormone activity.

Leptin and insulin levels fall, signalling an energy shortage and altering hunger and satiety cues.

Primary Driver:

Underfuelling (aka Low Energy Availability), whether intentional or unintentional.

The Fix:

Restore energy balance with adequate calories, carbohydrate availability, and recovery time.

2️⃣ Lactation

Population:

Postpartum individuals producing milk, whether two months or two years postpartum.

Mechanism:

Prolactin levels remain elevated to stimulate milk production, while estrogen and progesterone stay low to maintain lactation. This creates a hormonal profile surprisingly similar to perimenopause — low estrogen, disrupted sleep, and fatigue from both the demands of feeding and recovery from pregnancy.

Clinical Picture:

• Low estrogen symptoms such as vaginal dryness, mood changes, and irregular cycles

• Poor sleep from both hormonal shifts and infant care

• Increased appetite but sometimes inadequate intake

• Joint laxity and slower recovery

Key Hormones Affected:

Prolactin and oxytocin rise to stimulate milk production and let-down.

Estrogen and progesterone remain low.

Primary Driver:

A natural adaptation to milk production, which can be worsened by underfuelling or returning to high training loads too soon postpartum.

3️⃣ Perimenopause

Population:

Typically women aged 40 to 51, though it can begin as early as the mid-30s.

Mechanism:

Ovarian function becomes less predictable, leading to fluctuations in estrogen and progesterone. LH and FSH levels become erratic, often resulting in irregular or heavier cycles before they gradually decline.

Clinical Picture:

• Irregular or changing cycles

• Hot flashes and night sweats

• Mood and sleep disturbances

• Changes in body composition and recovery

• Often accompanied by increased life stress, reduced recovery time, and nutrition changes

Key Hormones Affected:

Estrogen fluctuates, then declines.

Progesterone often drops earlier.

FSH gradually increases over time.

Primary Driver:

The natural transition of ovarian aging, with symptoms influenced by lifestyle, stress, and nutrition.

Where They Cross Over

Here’s where things get complicated.

All three can cause:

• Fatigue and poor recovery

• Sleep disruption

• Reduced performance or motivation

• Irregular or absent menstrual cycles

• Changes in mood or cognition

• Reduced fertility

• Nutrient deficiencies such as low iron

• Reduced bone strength and higher risk of stress injuries

• Changes in body composition

Bottom line: All three conditions mimic each other and are worsened by inadequate fuelling.

This is why athletes and active women in any life phase need context, assessment, and sometimes advocacy. Being told you’re “in perimenopause” when you’re 28 and underfuelling, or that “it’s just hormones” when you’re 42 and training twice a day, misses the mark.

My Reality: Hormones, Kids, and Endurance

I’m 34, not in perimenopause.But I have two kids under three and a half, and in the past four years there’s been less than two weeks when I wasn’t pregnant or breastfeeding. That will probably continue for another couple of years..

Talk about hormonal fluctuations.

After more than two years of breastfeeding while training for endurance events, my body gave me plenty of signals to slow down and check in. I listened. And I truly believe that experience will set me up well for the menopause transition — though maybe that’s naïve?! Because physiologically, the lactation hormonal profile can have striking similarities to perimenopause, as we’ve discussed.

There’s limited data on masters athletes, and even less on lactating athletes. I think both groups can learn from each other while the research catches up to what women already know through lived experience.

Why Misinformation Hurts and the Harms of Social Media and Influencers

When someone suggests your symptoms can be fixed by a supplement, a high-protein diet, or a “blood sugar reset,” it’s not just misinformation — it’s a form of modern-day misogyny.

It minimizes your lived experience and distracts from the underlying issue.

You can’t supplement your way out of under-eating or overtraining. You can’t balance your hormones without fuelling adequately and respecting recovery.

So How Do You Start to Untangle It?

Start with:

✅ Reviewing your fueling — are you eating enough overall?

✅ Meeting daily macronutrient needs for training

✅ Checking carbohydrate timing around training

✅ Considering blood work such as a CBC, iron panel, thyroid panel, etc.

✅ Evaluating recovery, stress, and sleep

And if you’re not sure, reach out for professional support from a sports dietitian who understands physiology, training, and hormones. Because whether you’re 25, 35, or 45, the goal is the same: Fuel enough, train smart, and support your body’s changing needs.

Reflection Questions

Ask yourself (or your athletes):

• Are your periods irregular because of age, or could fuelling be playing a role?

• Are you experiencing bone stress injuries or repeated illness?

• Are you fuelling before and after training consistently?

• Are you feeling persistent fatigue despite unchanged training?

If these resonate, it might be time to look deeper than supplements — and start by eating enough.