How Underfueling Can Lead to Injury During Training: Nutrition Guidelines for Athletes
Why Fueling Matters for Athletes
Whether you're training for a marathon, hitting the gym, or practicing your sport daily, one factor can make or break your progress: fueling your body properly. Unfortunately, many athletes unintentionally underfuel, leading to fatigue, poor performance, and injury.
In this blog post, we’ll explain the connection between underfueling and injury risk and offer evidence-based guidelines for carbohydrate, protein, and fluid intake to keep you healthy and performing at your best.
What Is Underfueling?
Underfueling occurs when your energy intake (food and drink) doesn’t meet the demands of your training and daily activity. It can be intentional (e.g., dieting) or unintentional (e.g., busy schedule, poor appetite, or lack of nutrition knowledge).
How Underfueling Increases Injury Risk
If you consistently underfuel, your body won’t have the resources it needs to recover and adapt to training. This increases your injury risk in several key ways:
Increased risk of stress fractures due to impaired bone remodeling
Muscle breakdown and delayed recovery from lack of protein and energy
Weakened immune system, making it harder to stay consistent with training
Hormonal disruption (like reduced estrogen or testosterone), which affects both performance and recovery
Athletes who underfuel are more prone to overuse injuries like tendinitis, bone stress injuries (BSIs), and muscle strains.
Nutrition Guidelines to Prevent Injury
To stay strong and resilient during training, you need to focus on three key areas: carbohydrates, protein, and hydration.
1. Carbohydrates: Your Primary Source of Energy
Why they matter: Carbohydrates fuel high-intensity workouts and support glycogen stores. Low-carb diets can lead to fatigue and muscle breakdown.
Daily Carbohydrate Recommendations:
Training Load / Carb Intake (g/kg body weight)
Light (<1 hr/day) = 3–5 g/kg
Moderate (1–3 hrs/day) = 5–7 g/kg
High (>3 hrs/day)7–10+ g/kg
Example: A 70 kg athlete training 2 hours daily should consume 350–490g of carbs per day.
Best sources: Whole grains, fruits, starchy vegetables, rice, oats, pasta, and legumes.
2. Protein: Essential for Recovery and Repair
Why it matters: Protein supports muscle repair, immune function, and adaptation to training stress.
Daily Protein Recommendations:
Athlete Type / Protein Intake (g/kg body weight)
Endurance athletes = 1.2–1.6 g/kg
Strength athletes1.6–2.2 g/kg
Tip: Distribute protein intake evenly throughout the day, aiming for 20–30g every 3–4 hours.
Best sources: Lean meats, eggs, dairy, soy, legumes, protein shakes.
3. Hydration: Prevent Cramping and Fatigue
Why it matters: Dehydration affects performance, coordination, and injury risk. Even a 2% fluid loss can impair performance.
Fluid Intake Guidelines:
Before training: 5–10 mL/kg 2–4 hours prior
During training: 400–800 mL/hour, depending on sweat rate
After training: Rehydrate with 150% of fluid lost
Pro tip: Weigh yourself before and after long workouts to estimate sweat loss. Use sports drinks with electrolytes for workouts over an hour (it will also help replenish your carbohydrates!)
Signs You Might Be Underfueling
If you’re underfueling, your body will send you signals. Look out for these warning signs:
Frequent or nagging injuries
Ongoing fatigue or poor recovery
Loss of menstrual cycle (in females)
Increased illness or cold frequency
Mood changes and low energy availability
Constant hunger or fixation on food
Fuel Smart to Train Hard
If you're serious about your sport, nutrition should be a top priority. Proper fueling isn’t just about performance — it’s about injury prevention, long-term health, and sustainable training.
By meeting your needs for carbohydrates, protein, and hydration, you give your body the tools it needs to perform, recover, and stay injury-free.
Dr. Matt Wentzell
BKin, MSc, DC, FRCCSS(C)
North Vancouver Sport Chiropractor