The main running nutrition mistakes are drinking too much plain water, skipping carbohydrate during long runs, and eating too little for training load. The main form and training errors are overstriding, raising mileage too fast, and changing several workouts at once.
Exercise-associated hyponatremia means low blood sodium from excess plain water during prolonged running. Relative Energy Deficiency in Sport, called REDs, means the body lacks fuel for health and performance. Both conditions impair running and can harm health.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- Should you drink on a schedule?
- How much carbohydrate do long runs need?
- Are you eating enough for training?
- How fast should mileage rise?
- Are stride and workouts working against you?
Should you drink on a schedule?
Drink to thirst rather than on a fixed schedule during long runs. Large volumes of plain water can dilute blood sodium. The Wilderness Medical Society guidelines warn about this risk in the Wilderness Medical Society guidance.
Watch for bloating, puffy fingers, headache, and confusion. These signs point to exercise-associated hyponatremia. Stop and seek medical care if confusion develops.
- Bloating during a long run
- Puffy fingers or tight watch band
- Headache with excess drinking
- Confusion or disorientation
How much carbohydrate do long runs need?
Failing to take carbohydrate during long runs depletes glycogen and causes hitting the wall. Glycogen is stored carbohydrate in muscle and liver. Tufts sports nutrition guidance advises 30–60g of simple carbohydrates per hour on race day plus carb-loading for 3 days before a marathon, as described in the Tufts marathon fueling guidance. Higher intakes help many marathoners.
Marathoners who met 60–90g carbohydrate per hour were significantly more likely to finish under 3 hours in Seville Marathon research. The study authors reported the link at p=0.035, according to the Seville Marathon carbohydrate study. Many athletes still consume only about 32–52g per hour. That gap often explains late-race fading. Practice your hourly plan on long training runs.
Are you eating enough for training?
Chronically eating too little creates low energy availability. Experts define the risk zone as below 30 kcal per kg of fat-free mass. That shortage drives REDs and impairs performance, recovery, bone health, menstrual health, and immune health. You may feel tired, get sick often, or recover slowly.
Women may miss periods. Men may lose libido and bone density. Track intake against heavy weeks, not easy days. Add snacks around double sessions and long runs. Seek medical and nutrition care if symptoms persist.
How fast should mileage rise?
Increasing weekly mileage or intensity too quickly is a leading cause of overuse injuries. Prevention guidance caps increases at 10–20% per week. Cut other load or add rest when you add a long run, according to Loyola University Health System reporting in the Loyola runners injury prevention report. A sudden jump stresses tendons, bones, and joints.
Pain that alters form or lasts into the next run signals overload. Hold mileage steady for a week after hard races or illness. Plan one stressor per week. Keep most running easy while the long run grows. Rest days protect gains.
Are stride and workouts working against you?
Overstriding means the foot lands far ahead of the body's center. It often pairs with cadence near 160 steps per minute. That pattern raises braking forces and injury risk. Land the foot closer under the body.
A slightly quicker cadence can reduce reach. Keep the torso tall and steps quiet. Change only one training component at a time. For example, add just one interval session while raising mileage by 10–20%. Hold other workouts steady until the body adapts.