About

Women face unique physiological challenges during weight loss, particularly when preparing for bikini or figure competitions. The most critical risk is Relative Energy Deficiency in Sport (RED-S), formerly known as the Female Athlete Triad. When energy availability drops too low, the body shuts down non-essential functions, including the menstrual cycle (amenorrhea), bone density maintenance, and metabolic rate regulation.

This calculator is distinct because it doesn't just subtract 500 calories. It calculates your Energy Availability (EA)—the amount of dietary energy remaining for your body's functions after exercise training is subtracted. This ensures that while you get leaner, you stay above the critical threshold needed to maintain hormonal health. It prioritizes fat intake slightly higher than male calculators to support endocrine function.

Formulas

We use the Cunningham equation (based on Lean Body Mass) for higher accuracy in athletic women. The core safety metric is Energy Availability (EA):

EA = EI − EEELBM

Where EI is Energy Intake (kcal), EEE is Exercise Energy Expenditure, and LBM is Lean Body Mass (kg).

Reference Data

Energy Availability (EA)	Status	Physiological Impact
> 45 kcal/kg LBM	Optimal	Full hormonal function, bone health, muscle growth.
30 - 45 kcal/kg LBM	Sub-Clinical	Weight loss zone. Monitor for fatigue or cycle irregularities.
< 30 kcal/kg LBM	Critical Low (RED-S)	Reproductive suppression, bone loss, metabolic adaptation.
Nutrient	Min Threshold	Why?
Fats	0.8 g/kg bodyweight	Required for estrogen/progesterone synthesis.
Protein	2.0 g/kg LBM	Muscle retention during deficit.
Carbs	Variable	Balance of remaining calories for workout intensity.

Frequently Asked Questions

Relative Energy Deficiency in Sport represents a state where the body's energy intake is insufficient to support the energy expenditure required for health and daily activities, after the cost of exercise is taken into account. Symptoms include lost periods, stress fractures, and depression.

Women oxidize more fat during exercise than men and rely heavily on dietary fats for the production of sex hormones. Dropping fats too low (e.g., below 15-20% of calories) can rapidly lead to hormonal downregulation.

EEE is the calories burned strictly during your training session. For a typical hour of lifting, this might be 200-300 kcal. For cardio, it's whatever the machine or heart rate monitor estimates (often 300-500 kcal/hr). This calculator subtracts this from your food intake to see what's 'left over' for your organs.