Energy availability (EA) isn’t just a sports science term — it’s something that impacts all of us. EA is the energy your body has left to function after accounting for what you burn through daily activity and exercise.

When you don’t eat enough to cover those demands, your body doesn’t just lose weight — it may slow down metabolism, limit recovery, and make it harder to maintain lean muscle. Over time, chronically low energy availability can affect hormones, bone health, and overall vitality.

How We Measure It

There are two key ways to look at EA:

Calories per Lean Mass (FFM)

EA is calculated as calories per kilogram of fat-free mass.

Below 30 kcal/kg FFM per day is considered “low” and puts you at risk.

RMR Ratio

Compares your measured Resting Metabolic Rate (RMR) to a predicted RMR. If your measured RMR is less than 90% of predicted (<0.9), it signals your body may be adapting to underfueling.

What Does a Low RMR Ratio Mean?

An RMR ratio compares your measured resting metabolism to what we’d expect for your size and composition. When it falls below 0.9, your metabolism is running slower than expected — a red flag that your body is conserving energy.

Common causes include:

• Eating too little for your needs
• Long-term dieting or yo-yo dieting
• Training without enough fuel
• High stress or inadequate recovery

Why it matters:

• Harder fat loss (despite dieting)
• Trouble maintaining muscle
• Slower recovery and more fatigue
• Hormone or sleep disruptions

What the Research Shows

A 2025 study of 77 active women (from NCAA athletes to recreational exercisers) found:

• 63% weren’t eating enough (<30 kcal/kg FFM).
• 19% had suppressed metabolism (RMR ratio <0.9).
• 14% met both criteria — the highest risk group.

On average, participants also under-consumed carbohydrates. Researchers concluded that the RMR ratio may be a more practical tool than food logs, since self-tracking intake is often inaccurate.

Why It Matters Beyond Sports

Low energy availability isn’t just an athlete’s issue. Busy professionals, parents, and weekend warriors often underfuel by skipping meals, cutting calories too aggressively, or following restrictive diets.

Signs you may not be eating enough:

• Fatigue despite “doing everything right”
• Difficulty building or keeping muscle
• Plateaued weight loss
• Slow recovery from workouts
• Hormonal or sleep disruptions

Body Science Coaching’s Role

At Body Science Coaching, we don’t just test — we translate the data into action. Using your Resting Metabolic Rate, DEXA body composition, and lifestyle context, we can identify whether your metabolism is thriving or suppressed. From there, we build nutrition strategies to:

• Ensure energy availability is ≥30 kcal/kg FFM
• Keep your RMR ratio above 0.9
• Support lean mass, recovery, and long-term health
• Balance performance with sustainability

Our Recommendation

• Fuel for function: Don’t just eat less — eat to match your body’s true needs.
• Track your metabolism: Monitor changes with periodic RMR + DEXA testing.
• Turn data into action: Use personalized nutrition planning to avoid underfueling traps.

Bottom Line

Whether you want to perform better, stay strong as you age, or simply feel more energetic, fueling properly is essential. By combining advanced testing with targeted coaching, Body Science Coaching helps you stop guessing and start thriving.

👉 Ready to find out if you’re fueling enough? Work with our coaching team to interpret your test results and build a plan that supports your metabolism, performance, and long-term health.

Read about the Importance of Metabolic Flexibility

Metabolic Flexibility in Health & Disease