Practical, evidence-based nutrition recommendations for endurance and strength athletes: what to eat, when to eat it, and which supplements are actually worth considering.Key points
- Nutrition has three jobs in sport: fuel training, hydrate to protect performance, and recover so the next session counts.
- Needs are different for endurance (carbohydrate and fluid focus) and strength athletes (protein and total energy focus).
- A weight loss of more than 2% during exercise measurably reduces performance.
- Most athletes can meet their needs through food first. Supplements are the last 1 to 2%, not the foundation.
1. The basics: energy per gram
| Nutrient | Energy |
|---|---|
| Carbohydrate | 4 kcal per gram |
| Protein | 4 kcal per gram |
| Fat | 9 kcal per gram |
| Alcohol | 7.4 kcal per gram (no performance or recovery benefit) |
2. Hydration
The goal is simple: avoid losing more than 2% of body weight during exercise. Beyond this threshold, studies show reduced endurance performance, poorer balance control and a higher rate of perceived exertion (RPE).
Before exercise
400 to 600 mL (14 to 22 oz) of fluid, about 2 hours before.
During, under 1 hour
150 to 350 mL (5 to 12 oz) of water every 15 to 20 minutes. Sports drinks are not needed.
During, over 1 hour
A drink containing 6 to 8% carbohydrate plus electrolytes (sodium, chloride).
After exercise
Sports drinks help with rehydration, electrolyte replacement and muscle glycogen repletion.
3. General exercise recommendations
The American College of Sports Medicine (ACSM) recommends at least 3 sessions per week of about 40 minutes at moderate to vigorous intensity for fitness, and activity on most or all days of the week for general health. Strength gains are not compromised by adding endurance exercise to a resistance program.
4. Endurance athletes (low intensity, long duration)
Pre-exercise meal
- A meal or snack 3 to 4 hours before heavy training or competition may improve performance: it limits hunger, allows digestion and gastric emptying, and maximizes glycogen stores.
- A small meal 1 hour or less before does not appear to improve performance.
- Favor low glycemic index foods (GI under 55): blood glucose peaks around 90 minutes.
High-fat diets: a contested strategy
Some ultra-endurance athletes use a higher-fat diet (over 65% of energy) for at least 5 days before low-intensity, long-duration events to increase fat oxidation. Evidence shows this shifts fuel use, but it does not consistently improve performance and may reduce capacity at higher intensities. Treat it as an individualized experiment to test in training, never for the first time on race day.
Daily targets
| Component | Recommendation |
|---|---|
| Carbohydrate | 6 to 10 g/kg/day (about 55 to 70% of energy), scaled to training load |
| Protein | 1.2 to 1.4 g/kg/day (some guidelines allow up to 1.6 to 2.0 g/kg at high load or low energy availability) |
| Fat | May drop to 20 to 25% of energy to make room for carbohydrate |
| Vitamin C | 300 to 1000 mg/day. Higher doses may blunt training adaptations |
| Vitamin D | Typically about 50 µg/day (2000 IU) in some protocols; confirm with blood levels and clinical judgment |
| Caffeine | 1 to 6 mg/kg. Higher doses impair performance |
| Creatine | 2 to 3 g/day, regardless of body weight |
| Beta-alanine | 3.2 to 6.4 g/day, regardless of body weight |
During exercise longer than 1 hour
- 30 to 60 g of carbohydrate per hour, taken with fluids, to maintain blood glucose.
- Sports bars can help ultra-marathoners and other endurance athletes by replenishing glycogen and supporting protein balance. Take them with fluids to aid digestion and absorption.
- For very long efforts, intake can rise to 60 to 90 g/hour, but only if the gut has been trained to tolerate it (see our article on carbohydrate loading and gut training).
Post-exercise recovery
- Favor high glycemic index foods (GI over 70) to speed glycogen recovery: blood glucose peaks around 30 minutes.
- About 50 g of carbohydrate within 30 minutes enhances glycogen synthesis. Adding 10 to 15 g of protein boosts muscle protein synthesis and nitrogen balance compared with carbohydrate alone.
- Then 1.0 to 1.5 g/kg of carbohydrate over the following hours.
- Branched-chain amino acids (leucine, isoleucine, valine): leucine in particular has anabolic effects and supports recovery.
5. Strength athletes (high intensity, short duration)
Pre-exercise meal
The same principles apply: a meal 3 to 4 hours before is beneficial, a small meal within the last hour is not, and low glycemic index foods (GI under 55) are preferred.
Daily targets
| Component | Recommendation |
|---|---|
| Carbohydrate | 6 to 10 g/kg/day in the source guideline. Many strength athletes do well on 3 to 7 g/kg depending on training volume |
| Protein | 1.2 to 1.7 g/kg/day (10 to 35% of energy) |
| Fat | No more than 30% of energy (bodybuilders about 30%) |
| Vitamin C and D, caffeine, creatine, beta-alanine | Same ranges as for endurance athletes |
Protein powders and amino acids
- Protein requirements can be met through food alone. Powders and amino acid supplements are a convenience, not a necessity.
- Casein vs whey: whey raises blood amino acids for 1 to 2 hours, casein for about 7 hours. Casein is useful before sleep or long gaps between meals; total daily protein and leucine dose matter most.
Post-exercise recovery
Same strategy as for endurance athletes: high glycemic index foods, about 50 g of carbohydrate plus 10 to 15 g of protein within 30 minutes, and leucine-rich protein sources.
6. Supplements: what is worth considering?
Caffeine
1 to 6 mg/kg improves performance. Higher doses do not help and may harm (anxiety, GI upset, sleep loss).
Creatine
2 to 3 g/day. One of the most studied supplements, mainly useful for high-intensity efforts.
Beta-alanine
3.2 to 6.4 g/day. Buffers acidity in high-intensity efforts. May cause harmless tingling.
Vitamins C and D
Correct deficiencies, not more. High vitamin C may impair adaptation. Check vitamin D blood levels.
Supplement safety
Supplements are poorly regulated and can contain banned substances. Competitive athletes subject to anti-doping rules should use third-party tested products only.
7. When to seek professional advice
- Unintentional weight loss, repeated stress fractures or illness, menstrual irregularities (possible RED-S, low energy availability).
- Persistent digestive problems during exercise despite gut training.
- Fatigue, performance decline or poor recovery despite adequate rest.
- Any restrictive eating pattern or unhealthy relationship with food.
Disclaimer: This page is for educational purposes only and does not replace individualized advice from a physician or registered sports dietitian. Needs vary by sport, training load, body composition and health status.