5 nutrition rules that do not apply to runners

By Sarah Lee · 2026-08-16

Someone in a running forum put it better than I have managed to: there is a lot of nutrition advice that applies decently well to the general population, but not to runners.

That is the whole problem in one sentence. Most of what follows is not wrong in the way that a myth is wrong. It is advice built for a body that is not doing what yours is doing, and then handed over anyway.

Five of them. I picked these five because I can point at a full text for each. There are more, and some of the more interesting ones I had to leave out precisely because I could not source them.

1. Cut back on the carbs

Fine as general advice for someone whose training load is a brisk walk. In a training block it works against the mechanism.

The joint position paper from the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine sets carbohydrate targets that scale up with training volume.¹ But the finding that matters most for this audience is in a separate review of post-exercise glycogen resynthesis: female subjects showed substantial enhancement of muscle glycogen storage from increased carbohydrate intake only after total energy intake was also increased.²

That is a specific and slightly awkward result. Moving carbohydrate around inside the same total did not produce the effect. The total had to come up too.

2. Do not eat before exercise

The general-population version of this has a logic to it, roughly about not exercising on a full stomach.

The position paper describes a pre-event meal and characterizes what it should look like: low-fat, low-fiber, low-to-moderate protein, because that composition is less prone to cause gastrointestinal problems and promotes gastric emptying.¹ The guidance is about what and when, not whether.

Worth separating two things that get merged here. Arriving at a session under-fueled and arriving at it uncomfortably full are different failures, and the advice only addresses one of them.

3. Whole grain is always the better choice

This is the one that surprises people, and it is graded.

The position paper's Evidence Analysis Library rated it Grade I, Good: when conditions were matched for carbohydrate and energy, neither glycemic index nor glycemic load affected endurance performance or metabolic responses.¹ Matched for carbohydrate and energy, the type did not change the outcome.

The place a real difference shows up is comfort, and it points the opposite way from the advice: lower-fiber choices sit easier close to a session.¹ So the rule is not merely inapplicable here, it is backwards for one specific slot in the day.

None of which makes whole grains a problem. Neither list is better. It is that the rule was imported from a context where the goal was different.

4. Electrolytes are a marketing scam

Half right, and the half that is right is doing a lot of work.

Independent position statements agree that replacing sodium does not require a special product and that a normally varied diet generally covers it. The National Athletic Trainers' Association statement is the best-evidenced source in that set.³ So yes, the category is oversold, and most people most of the time are fine without anything added to their fluids.

The exception is the population reading this. After a long or hot session, water with sodium alongside it is retained better than water on its own.³ Endurance runners in heat are one of the groups where it stops being theater.

I would also flag that your own sweat sodium is not a knowable quantity by looking at your shirt. In a review pooling roughly five hundred athletes including about a hundred women, local sweat sodium concentration ranged across roughly 10 to 90 millimoles per liter, and sex did not significantly explain the variation.⁴ White marks on kit have never been validated as a measurement, and residue tracks sweat volume and evaporation as much as concentration.

5. Drink more water, you are probably dehydrated

The most confidently repeated one, and the only entry on this list where the general-population version carries its own risk when you scale it up.

The NATA statement makes it a graded recommendation, SORT evidence level A: individuals should not gain body mass during exercise, and hyperhydration confers no physiological or performance advantages.³ Gaining mass during a session is the thing being warned against, and drinking past thirst is how you get there.

The joint position paper adds a note specific to this audience: women generally have smaller body size and lower sweat rates and appear to be at greater risk of over-drinking.¹ I will hold that one loosely, because in at least one large marathon dataset the sex difference disappeared after adjusting for body mass index and finishing time. The direction of the caution stands; the mechanism behind it is less settled than it sounds.

There is no universal number of cups. That is not evasion, it is the finding.

The one I could not include

The rule I most wanted on this list was the one about not eating carbohydrate at night, because it comes up constantly and because I have seen the exact opposite claimed with equal confidence.

I could not find a full text I would stand behind in either direction, so it is not here. This site does not run numbers read from an abstract, and that has to include the numbers I would enjoy having.

Which is, incidentally, the actual point of the list. Advice built for the general population is not usually a lie. It is a claim that quietly carries a population with it, and the population is not you.

Sources

1. Thomas DT, Erdman KA, Burke LM. 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 2016;116(3):501-528. Joint position paper and evidence review; population is athletes broadly. Pre-event menu composition quoted verbatim; the glycemic index finding carries its Evidence Analysis Library grading of I (Good). Read in full text. DOI: 10.1016/j.jand.2015.12.006
2. Burke LM, van Loon LJC, Hawley JA. Postexercise muscle glycogen resynthesis in humans. Journal of Applied Physiology 2017;122(5):1055-1067. Narrative review. Female-specific finding cited here: substantial enhancement of muscle glycogen storage with increased carbohydrate intake occurred only after total energy intake was also increased. Read in full text. PMID 27789774. DOI: 10.1152/japplphysiol.00860.2016
3. McDermott BP, Anderson SA, Armstrong LE, et al. National Athletic Trainers' Association Position Statement: Fluid Replacement for the Physically Active. Journal of Athletic Training 2017;52(9):877-895. Position statement with graded recommendations; the no-mass-gain and no-hyperhydration-advantage recommendation is Recommendation 6 at SORT evidence grade A. Read in full text. DOI: 10.4085/1062-6050-52.9.02
4. Baker LB. Sweating Rate and Sweat Sodium Concentration in Athletes: A Review of Methodology and Intra/Interindividual Variability. Sports Medicine 2017;47(Suppl 1):111-128. Review; approximately 500 athletes pooled, including approximately 100 women. Local sweat sodium concentration ranged roughly 10-90 mmol/L; sex did not significantly explain the variation; day-to-day whole-body variation within an individual approximately 5-7%. Regional patch and whole-body washdown are different instruments and are not interchangeable. Read in full text. PMC5371639. DOI: 10.1007/s40279-017-0691-5