What Energy Availability Actually Is (And Why Women Who Train Hard Keep Missing It)

If you train hard, eat “well,” and still feel flat, puffy, exhausted, or stuck — this blog is for you.

Because for most women who lift, run, do HYROX, classes, or endurance-style training, the issue is not discipline.

And it’s not that you “need to eat less.”

It’s that your body doesn’t have enough usable energy available to do what you’re asking of it.

This is called energy availability and it’s one of the most misunderstood concepts in female performance and fat loss.

First: what is energy availability?

Energy availability is not how many calories you eat.

It’s how much energy your body has left over after training to run basic functions.

In simple terms:

Energy availability = energy eaten – energy used in training

What’s left is what your body uses for:

• Hormone production

• Recovery and repair

• Digestion

• Sleep quality

• Mood and focus

• Immune function

So you can technically be eating plenty of calories……and still be under-fuelled.

The analogy I always use (because it makes this click)

Think of your body like a phone battery.

Training drains the battery.Food recharges it.

Energy availability is the percentage you leave the battery on.

If your phone lives at 5–10%, it goes into low power mode:

• Screen dims

• Apps shut down

• Performance drops

Your body does the same thing.

Not because it’s broken but because it’s protecting you.

Why high calories don’t automatically mean high energy availability

This is where most women get confused.

I’ve worked with clients eating 2,600–2,800 calories who were still showing signs of low energy availability:

• Constant fatigue

• Puffiness and inflammation

• Poor recovery

• Emotional volatility

• Flat training sessions

• Recurrent niggles or injuries

On paper, they weren’t under-eating.

But their bodies were still behaving like they were.

Why?

Because the fuel wasn’t accessible for the work they were doing.

Calories matter but fuel source matters just as much

High-intensity training (running, HYROX, intervals, hard strength sessions) runs primarily on glycogen.

Glycogen comes from carbohydrates.

Protein and fat are important, but they are not fast fuel.

So when someone is:

• Eating high protein

• High fat

• High fibre

• Low carbohydrate

…while training intensely, the body still perceives energy scarcity, even if calories are high.

You can eat 500 calories before a session, but if it’s mostly fat and protein, your muscles still feel under-fuelled.

That leads to:

• Elevated stress hormones

• Poor output

• Slower recovery

• Water retention

• Increased hunger later

This is how women end up saying:

“I’m eating more… and I feel worse.”

Under-fuelling doesn’t always look like eating less

This is the part diet culture misses.

Under-fuelling often shows up as mismatch, not restriction.

1. Timing under-fuelling

No carbs before sessions.Training fasted or semi-fasted.“Saving” food for later.

2. Distribution under-fuelling

Low intake midweek → hard trainingOvereating at weekends → less training

The body never gets a clear signal.

3. Macro under-fuelling

Calories high, carbs low.Fueling endurance and intensity with fats and protein.

4. Recovery under-fuelling

No carbs or protein post-session.Poor sleep.No true rest days.

What low energy availability actually feels like

Most women don’t recognise it because it’s been normalised.

Common signs:

• Feeling flat despite “eating well”

• Puffiness and water retention

• Poor sleep despite enough hours in bed

• Irritability or emotional volatility

• Constant cravings

• Training that feels hard but doesn’t progress

• Repeated injuries or niggles

• “Wired but tired” energy

These are not personality flaws.

They are physiological signals.

Why “just eating more” often backfires

When women come from dieting backgrounds, increasing calories usually means:

• More protein

• “Healthier” foods

• Higher fibre

• Eating away from training

So calories go up… but energy availability doesn’t.

Training still feels flat. Recovery still suffers.Weight may increase, without feeling better.

That’s when fear of food creeps in.

Not because food is the problem but because the strategy is wrong.

Fuel for the work required (and why this changes everything)

A principle widely used in performance nutrition (and talked about by James Morton) is fuel for the work required.

It means:

• Not every day needs the same fuel

• Hard days need more accessible carbs

• Rest days still need enough to recover

• Protein stays consistent, not obsessive

• Carbs rise and fall with intensity

This approach creates flexibility, not restriction.

You stop eating blindly.You start eating with intent.

When energy availability is restored, everything changes

When fuel matches demand:

• Training quality improves

• Recovery improves

• Hunger settles

• Hormones stabilise

• Body composition follows, without dieting harder

This is the difference between working against your body and working with it.

Why this matters

Most women don’t need more willpower.They need structure.

Fuel Her Fire was built around this exact problem:

• Women who train hard

• Eat “well”

• But feel flat, stuck, and frustrated

It teaches:

• How to fuel training properly

• How to periodise nutrition with training

• How to stop under-fuelling without overeating

• How to trust your body again

You’re not broken.You’re just under-fuelled in the wrong places.