The most dangerous nutritional problem in female fitness is under-eating around training. Not deliberately — most women don't realise they're doing it. They diet the same way they've always been taught to diet, unaware that their training volume has fundamentally changed their nutritional requirements.
This isn't vanity advice. This is survival advice.
The RED-S Problem: Relative Energy Deficiency in Sport
RED-S (Relative Energy Deficiency in Sport) occurs when someone trains hard but doesn't eat enough to support that training. The consequences are serious:
- Loss of menstrual cycle (or irregular cycles)
- Declining strength despite increased training
- Persistent fatigue and poor recovery
- Weakened immune system (getting sick constantly)
- Decreased bone density (stress fracture risk)
- Hormonal suppression (low oestrogen, low thyroid)
Most women attributing these issues to "their body" or "getting older" are actually just underfed relative to their training demands.
The fix is simple: eat more. Specifically, eat enough to support training while maintaining hormonal health.
Protein: The Non-Negotiable
Current evidence: 1.6–2.2 g per kilogram of body weight per day for women training hard (resistance training 3+ times per week).
Most dietary guidelines show 0.8 g/kg, which is the RDA for sedentary people. If you're lifting, that's insufficient.
Why higher protein matters:
- Muscle protein synthesis requires amino acid availability. Higher training stress increases the demand for amino acids to rebuild and adapt muscle tissue.
- Higher protein preserves muscle during periods of calorie deficit, which is critical for body recomposition.
- Protein has the highest thermic effect of food (uses calories just to digest), so it supports fat loss while maintaining muscle.
- Higher protein intake stabilises blood sugar and supports satiety, making it easier to stick to a diet.
For a 65 kg woman:
- Minimum: 104 g daily
- Optimal for training: 130–143 g daily
How to hit this:
- 40 g from a protein source at breakfast (Greek yoghurt, eggs, cottage cheese)
- 30 g at lunch (chicken, fish, tofu)
- 30 g at dinner (beef, salmon, legumes)
- 20 g from snacks (protein shake, cheese, nuts)
Spread protein across meals. Your body utilises 20–40 g per meal more efficiently than larger boluses.
Carbohydrates: Essential, Not Evil
This is where women's training often fails. They train intensely 4 days per week while restricting carbohydrates, believing it'll accelerate fat loss.
Result: low energy in training, poor performance, slower recovery, hormonal disruption.
Carbohydrates fuel training. They replenish muscle glycogen, support hormonal health, and enable recovery between sessions.
Carbohydrate targets for female athletes:
- Light activity days: 3–4 g/kg
- Moderate training days: 4–6 g/kg
- High training volume days: 6–8 g/kg
For a 65 kg woman training 4 days per week:
- Rest days: ~195–260 g carbohydrates
- Training days: ~260–390 g carbohydrates
This varies significantly based on your specific training and individual metabolism, but these are sensible starting points.
Why carbs protect your menstrual cycle:
Low carbohydrate intake paired with high training volume suppresses oestrogen production. Your body interprets the metabolic stress as famine and shuts down non-essential functions (including reproduction). This is not a personal failing — it's survival physiology.
Higher carbohydrate intake supports oestrogen synthesis and maintains regular menstrual cycles. This is particularly important during the luteal phase (second half of cycle) when calorie and carbohydrate needs increase.
Practical sources: Oats, rice, potatoes, pasta, bread, fruit, vegetables. Quality varies, but quantity is what matters for training support.
Fats: The Hormone Builders
Minimum 20–25% of total calories from fat. For a 2000 kcal diet, that's 44–56 g of fat daily.
Why? Cholesterol is the precursor for all sex hormone synthesis (oestrogen, progesterone, testosterone). Chronically low fat intake suppresses hormone production.
Additionally, fat-soluble vitamins (A, D, E, K) require dietary fat for absorption. These are critical for immune function, bone health, and recovery.
You don't need excessive fat. Just don't fear it.
Practical sources: Olive oil, nuts, seeds, avocado, fatty fish, eggs, full-fat dairy. Include these regularly, not obsessively.
Pre and Post-Workout Nutrition
Before Training (1–2 hours prior):
- Carbohydrates: 1–2 g/kg (easier digestion)
- Protein: 0.2–0.4 g/kg
- Minimal fat and fibre (slows digestion)
Example: Banana with peanut butter, or toast with honey.
After Training (within 2 hours):
- Protein: 0.25–0.4 g/kg
- Carbohydrates: 1–1.5 g/kg
- Some fat is fine
Example: Chicken and rice, Greek yoghurt with berries, protein shake with oats.
This isn't magic. The evidence shows benefits are marginal if total daily protein and carbs are adequate. But it supports performance and recovery, so it's worth doing.
The Menstrual Cycle and Nutrition
Your nutritional needs shift across your menstrual cycle.
Follicular Phase (Days 1–14, approximately):
- Oestrogen rising
- Lower calorie and carbohydrate needs
- Metabolism slightly lower
- Training often feels easier
Nutrition: Maintenance calories, normal carb intake (4–6 g/kg), adequate protein.
Luteal Phase (Days 15–28, approximately):
- Progesterone rising
- Higher calorie needs (100–300 kcal/day more)
- Higher carbohydrate needs
- Training often feels harder, metabolic rate elevated
Nutrition: Slight calorie increase, increase carbohydrates to the higher end (6–8 g/kg), maintain or increase protein, prioritise easy digestion.
This isn't overly complicated — track your cycle and adjust your carbs/calories slightly. Women who do this often notice better training performance, less hunger, and easier body composition management.
Supplements for Women Who Train
Creatine Monohydrate — 3 g daily
This is criminally underused in women. The evidence in female athletes shows:
- Increased strength (particularly useful for strength athletes and hypertrophy)
- Improved body composition (modest but consistent)
- Cognitive benefits (memory, processing speed)
- Well-tolerated, safe, evidence-backed
Creatine is not a steroid. It's a compound naturally found in meat that increases phosphocreatine availability in muscle, supporting ATP regeneration during high-intensity effort. It's also the most research-backed supplement in existence.
Dose: 3 g daily, every day. No loading required (loading shortens the timeline slightly but isn't necessary).
Protein Powder
Convenient, cost-effective, and practical. Whey, casein, plant-based — all work if total daily protein is adequate. Choose based on digestion tolerance and taste preference.
Vitamin D
If you live in the UK or don't get adequate sun exposure, vitamin D supplementation is sensible. Current evidence suggests 1000–2000 IU daily for most women, more if deficient.
Critical for immune function, bone health, and mood. Get your levels tested if you're supplement-curious.
Iron
Only if deficient. Women lose iron through menstruation. If you're experiencing persistent fatigue, low energy, poor recovery, get your iron levels checked. Supplementing without deficiency is unnecessary and potentially problematic.
Electrolytes
If training long sessions (90+ minutes) or in hot conditions, electrolyte drinks (sodium, potassium, carbohydrates) support hydration and performance. Otherwise, normal diet provides sufficient electrolytes.
Practical Nutrition Framework
Daily targets for a 65 kg woman training 4 days per week:
- Protein: 130–143 g (1.8–2.2 g/kg)
- Carbohydrates: 260–390 g (4–6 g/kg depending on training)
- Fats: 50–65 g (25–30% of calories)
- Total calories: ~2200–2400 kcal
Implementation:
- Pick a protein target and hit it daily
- Eat carbs around training for performance
- Include fat sources daily
- Fill remaining calories with whole foods
- Supplement with creatine and vitamin D
- Track weight weekly — adjust calories if not progressing as expected
When to Adjust Calories
If losing weight too quickly (>0.5 kg per week): Add 100–200 kcal daily. You're in too large a deficit.
If weight stuck: First ensure protein is adequate and consistency is real (tracking 2+ weeks). If yes, reduce calories 100–200 kcal and reassess in 2 weeks.
If strength declining despite adequate training: You're likely underfed. Add calories, particularly carbohydrates.
The Bottom Line
Women who train hard require more food than women who don't. Proper nutrition — adequate protein, sufficient carbohydrates, consistent fats, and sensible supplementation — is not optional. It's the difference between progress and stagnation, between hormonal health and RED-S.
The physique you're building requires fuel. Eat like an athlete.
References:
Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Journal of the Academy of Nutrition and Dietetics, 116(12), 39–54.
Smith-Ryan, A. E., Melvin, M. N., Wingfield, H. L., & Woessner, M. N. (2014). High-Dose Creatine Supplementation Does Not Increase Muscle Mass or Strength in Female Athletes. Journal of the International Society of Sports Nutrition, 11(1), 54.
Seb coaches aesthetics-focused training for men and women. He works with busy professionals to build strength, muscle, and confidence through evidence-based programming and practical nutrition advice.