Why Underfuelling Could Be Holding You Back

You’re exercising regularly. You’re trying to make healthy food choices. You’re committed to your goals. Yet you’re constantly tired, struggling to recover and wondering why your body isn’t responding the way you expected.

Sound familiar?

For many women, the first instinct is to eat less or train harder. But what if the opposite is true?

As a Clinical Nutritionist, I often see women who are unintentionally underfueling their bodies. They’re walking daily, strength training, running, attending Pilates or F45 classes, juggling busy careers and family life, yet they’re simply not eating enough to support the demands they’re placing on their bodies.

The result? Fatigue, poor recovery, hormone disruption and declining performance – both in the gym and in everyday life.

What is Low Energy Availability?

Low Energy Availability (LEA) occurs when your body doesn’t have enough energy available to support both exercise and normal physiological function (Burke et al., 2024).

Think of your body as having an energy budget.

Every day, you deposit energy through food. You also expend energy through exercise, work, walking the dog, chasing the kids, and countless other tasks that make up daily life.

Once those energy demands have been met, your body still needs enough left over to support essential functions like:

• Hormone production
• Brain function
• Muscle repair and recovery
• Bone remodelling
• Digestion
• Immune function
• Cardiovascular health
• Reproductive health

When there isn’t enough energy left over, your body starts conserving resources. It essentially says, “I don’t have enough fuel to keep everything running optimally, so I’ll prioritise survival.”

Initially, these changes can be subtle. Over time, however, they can begin to affect multiple body systems (Cabre et al., 2022).

When Low Energy Availability Becomes RED-S

If low energy availability becomes prolonged or severe, it can develop into Relative Energy Deficiency in Sport (RED-S).

Despite the name, RED-S isn’t just something that affects elite athletes.

The International Olympic Committee defines RED-S as a syndrome caused by problematic low energy availability that affects multiple aspects of health and performance (Burke et al., 2024).

RED-S can influence:

• Hormonal health
• Bone health
• Metabolic function
• Gastrointestinal health
• Immune function
• Cardiovascular health
• Mental wellbeing
• Recovery and exercise performance

A helpful way to think about it is this:

• Low Energy Availability (LEA) is the cause.
• RED-S is the collection of health consequences that may develop if LEA isn’t addressed.
• It’s Not Just Elite Athletes

One of the biggest misconceptions surrounding RED-S is that it only affects professional athletes. In reality, I think we’re probably missing many women because they don’t fit the stereotypical image.

You might be at risk if you:

• Exercise most days of the week.
• Are trying to lose weight while increasing your training.
• Skip meals because you’re busy.
• Avoid carbohydrates.
• Have a physically demanding job.
• Follow restrictive diets.
• Feel guilty when you miss a workout.
• Regularly push through fatigue.

Many women aren’t intentionally restricting food – they’re simply underestimating how much fuel their body actually needs (Cabre et al., 2022).

Signs You May Be Underfueling

Your body is incredibly clever. When it doesn’t receive enough energy, it starts making compromises.

Some of the signs of low energy availability include:

• Persistent fatigue
• Poor recovery after exercise
• Declining performance
• Frequent illness
• Increased injuries or stress fractures
• Feeling cold
• Brain fog
• Mood changes
• Hair loss
• Constant food cravings
• Menstrual changes or loss of your period

It’s easy to dismiss these symptoms as stress, ageing, or simply training harder than usual. However, they’re often your body’s way of telling you that it doesn’t have the resources it needs. Loss of your menstrual cycle, in particular, should never be considered a normal consequence of exercising. It’s an important clinical sign that deserves investigation. Emerging research also suggests that a history of RED-S may have implications beyond athletic performance. Early evidence indicates that women with a history of RED-S may have an increased risk of certain pregnancy complications, including preterm labour and preterm birth. While further research is needed, it reinforces the importance of recognising and treating low energy availability early (Jones et al., 2025).

Eating More Is Part of the Solution—But So Is Fueling Well

One of the hardest conversations I have with women is telling them they may actually need to eat more. After years of dieting and hearing messages like “eat less and move more,” this can feel completely counterintuitive. Recovering from low energy availability isn’t simply about increasing calories – it’s also about fuelling your body with the right balance of protein, carbohydrates and healthy fats, alongside essential vitamins and minerals, to support normal physiological function.

For example:

• Carbohydrates replenish glycogen stores, fuel exercise and support brain function.
• Protein helps repair muscle, supports immune function and maintains lean body mass.
• Healthy fats are essential for hormone production, cell health and the absorption of fat-soluble vitamins.
• Micronutrients such as iron, calcium, vitamin D, magnesium and the B-group vitamins play vital roles in energy production, oxygen transport, bone health, muscle function and recovery.

Simply increasing portion sizes without considering nutrient quality is unlikely to capture the whole picture. Likewise, eating an extremely nutrient-dense diet but not consuming enough overall energy can still leave your body underfuelled.

Every meal provides your body with the energy and nutrients it needs to produce hormones, repair tissues, support your immune system, maintain bone health and recover from the demands of everyday life.

How We Support Women at Katie Blakely Wellness

At Katie Blakely Wellness, we don’t just look at what you’re eating – we look at whether you’re eating enough to support your body, your lifestyle and your goals.

That may include assessing:

• Your energy intake in relation to your training and daily energy expenditure.
• Meal timing before and after exercise.
• Protein, carbohydrate and healthy fat intake.
• Potential micronutrient deficiencies.
• Menstrual health.
• Recovery, sleep and stress.
• Gastrointestinal symptoms.
• Relevant blood test results.

Rather than focusing solely on weight or calories, we take a whole-body approach. Because optimal nutrition isn’t just about improving your performance in the gym—it’s about supporting your hormones, bones, brain, gut, immune system and long-term health.

When your body is properly fuelled, you’re giving it the resources it needs to recover, adapt and thrive.

The Bottom Line

If you’ve been training hard but feeling flat, don’t assume you need to eat less or push yourself harder.

Instead, ask yourself:

“Am I giving my body enough energy and enough nutrients to support everything I’m asking it to do?”

Sometimes, the missing piece isn’t more discipline. It’s more fuel.

If you’re concerned that you may be underfueling or you’re experiencing symptoms such as fatigue, poor recovery or menstrual changes, working with a qualified Clinical Nutritionist can help identify the underlying cause and develop a personalised plan that supports both your health and your performance. Both in our Women’s Health Clinic in Croydon & Online Australia-Wide, I offer 1:1 holistic support to help assess what’s causing your symptoms, and get to the bottom of it with a mixture of diet, lifestyle and supplement advice. If you’d like to chat more, book in a free 15 minute discovery call to learn more.