Athletes’ Nutritional Demands: What the Evidence Actually Recommends

Endurance performance is constrained less by motivation and more by physiology: energy availability, glycogen stores, recovery capacity, and hydration status. The narrative review by Amawi et al. (2024) synthesizes current sports-nutrition guidelines to clarify what athletes actually need to eat and drink to support performance, recovery, and long-term health. Importantly, this paper does not promote novel strategies; it consolidates established, evidence-based intake ranges.

What the Science Looked At

The authors conducted a narrative review of experimental and observational studies in athletic populations, drawing on consensus statements from major sports-nutrition organizations. The focus was on:

• Energy availability
• Carbohydrate, protein, and fat intake
• Hydration and electrolytes
• Supplements with proven ergogenic effects

The aim was to summarize current quantitative recommendations, not to test new interventions.

What Was Found — With Concrete Intake Values

1. Energy and Energy Availability

The review emphasizes that many endurance athletes fail to meet total energy needs, especially during high training volumes. However, no fixed kcal/kg recommendation is provided; intake must scale with training load, body size, and sport demands.

What this means: The paper supports adequacy of energy intake but does not define a universal calorie target.

2. Carbohydrates: Primary Performance Fuel

The review provides clear quantitative carbohydrate recommendations:

• General daily intake:
  5–12 g carbohydrate per kg body weight per day
• High training volume (>12 h/week, moderate–high intensity):
  8–10 g/kg/day is recommended to maximize muscle glycogen stores

The review explicitly notes that percentage-based recommendations (e.g., “60–70% of calories”) are no longer favored, as they fail to scale with total energy intake.

Physiological context provided:

• Liver glycogen stores: ~80–100 g
• Skeletal muscle glycogen stores: ~300–400 g
  These limited stores explain why under-fueling rapidly impairs performance.

3. Protein: Daily Needs and Post-Exercise Dosing

The paper provides both daily and per-meal protein recommendations.

Daily protein intake (g/kg body weight):

• Endurance athletes: 1.2–2.0 g/kg/day
• Strength-focused training: 1.6–2.8 g/kg/day
• Muscle gain: 1.6–2.2 g/kg/day
• Energy deficit: 2.3–3.1 g/kg fat-free mass

These ranges are summarized directly in the review’s Table 2.

Post-exercise protein intake:

• 0.31 g/kg body weight per meal
• Protein should be high-quality and rapidly digestible (e.g., whey)
• A carbohydrate-to-protein ratio of ~4:1 post-exercise is recommended to support glycogen resynthesis

The review notes that exercise elevates anabolic sensitivity for at least 24 hours, but does not prescribe exact timing windows beyond practical tolerance.

4. Fat Intake

The review provides clear percentage-based guidance for fat:

• Total fat intake: 20–35% of total energy intake
• Saturated fat: <10% of total energy

High-fat or fat-loading diets (>65% of calories from fat) may increase fat oxidation but do not improve performance and may impair high-intensity output.

5. Hydration and Electrolytes

The review discusses hydration strategies but offers limited prescriptive intake values.

Key quantitative points:

• Sports drinks are most appropriate during:
  • Exercise >1 hour
  • Hot/humid conditions
  • Heavy or salty sweating
• Sodium concentration effects:
  • ~20 mmol sodium: may not outperform water
  • ~45 mmol sodium: associated with greater fluid retention (higher hydration index)

The authors emphasize that minimum effective sodium doses remain uncertain and require further research.

6. Omega-3 Fatty Acids

Unlike many supplements, omega-3 intake is quantified:

• Recommended dose: 450–900 mg/day
• Upper safe limit: up to 3 g/day

Omega-3s are discussed in relation to inflammation modulation and muscle health, not as direct performance enhancers.

7. Ergogenic Aids

Among supplements, only a few are identified as performance-enhancing:

• Creatine
• Caffeine
• Sodium bicarbonate

The review does not provide dosing protocols for these aids, focusing instead on evidence of efficacy and contamination risk.

What This Means for Endurance Athletes (Evidence-Bound)

Based strictly on the review:

• Daily carbohydrate intake should be scaled to training load, not calories or food percentages.
• Protein needs are higher than general-population norms, with specific g/kg ranges depending on training type.
• Post-exercise nutrition is quantitatively defined and matters for both glycogen and muscle repair.
• Fat intake should remain moderate; extreme fat-loading strategies are not supported for performance.
• Hydration strategy should be context-specific; sodium needs are not precisely defined.
• Supplement use should be conservative and evidence-based.

What This Does Not Mean

• The review does not prescribe individualized meal plans.
• It does not define exact timing windows for carbohydrate intake during exercise.
• It does not provide sport-specific fueling protocols (e.g., grams per hour during races).
• It does not justify aggressive supplementation beyond basic needs.

Bottom Line

This review reinforces a central message:
Performance nutrition is not about trends, but about meeting clearly defined intake ranges — especially for carbohydrates and protein — that scale with training demands.

Where the evidence is strong, the authors provide numbers.
Where it is not, they explicitly refrain from doing so.

That restraint is the strength of the paper.

Source: Amawi A, AlKasasbeh W, Jaradat M, Almasri A, Alobaidi S, Hammad AA, Bishtawi T, Fataftah B, Turk N, Saoud HA, Jarrar A and Ghazzawi H (2024) Athletes’ nutritional demands: a narrative review of nutritional requirements. Front. Nutr. 10:1331854. doi: 10.3389/fnut.2023.1331854