When your calories are too low, your body might start cutting corners where it counts most.
Energy Availability (EA) measures how much energy is left for essential functions after accounting for calories burned through exercise.
It’s calculated as:
EA = (Energy Intake – Exercise Energy Expenditure) ÷ Fat-Free Mass (FFM)
In simple terms:
How much energy is left to fuel recovery, hormone production, brain function, immune health (and more) beyond just covering your training?
This post highlights that hitting your macros isn’t enough if EA is too low. Even a well-tracked diet can fail if there’s not enough energy to sustain normal body functions.
Example – Low EA:
Sarah weighs 60 kg with ~45 kg fat-free mass. She eats 1,600 kcal/day and burns ~600 kcal through training.
EA = (1600 – 600) ÷ 45 = ~22 kcal/kg FFM/day, firmly in the low EA risk zone. Despite tracking macros, Sarah’s recovery, hormones and performance are at risk.
🔴 Low EA (<30 kcal/kg FFM/day):
Danger zone.
Hormonal disruptions, impaired metabolism, muscle loss, neurological issues, menstrual dysfunction (females), low libido (males), and long-term health risks.
🟠 Reduced EA (30–44 kcal/kg FFM/day):
Risk zone.
May allow short-term performance but increases risk of hormonal suppression, fatigue, metabolic slowdown and impaired recovery.
Should only be used strategically for short periods (such as during fat loss phases).
🟢 Optimal EA (≥45 kcal/kg FFM/day):
Optimal zone.
Supports muscle growth, recovery, hormone balance, mood, cognitive function, bone health and maintains metabolic rate.
Spend the majority of training cycles in this range.
Bottom line: Even if you track macros perfectly, low EA means your body will struggle to recover, adapt and perform. Long-term success depends on maintaining adequate EA, not just hitting calorie targets.
Prioritising optimal EA is essential for performance, recovery, health and longevity. While dipping lower may be necessary for specific sport goals (like comp prep), it should always be done with caution and close monitoring. Your health depends on it.