Carb Loading Is a Lie (And 6 Other Running Nutrition Myths That Are Hurting Your Training)

Running nutrition is full of advice that sounds logical, gets repeated endlessly, and is mostly wrong.

You've heard it all: carb load the night before your race, run fasted to burn fat, drink before you're thirsty, take a protein shake within 30 minutes. This advice has been repeated so often that it's become gospel — passed from training partner to training partner, pinned in running forums, repeated by influencers who've never read a single sports nutrition study.

Let's fix that. Here are seven running nutrition myths that are actively hurting your training — and what the research actually says.

The classic image: the night before a marathon, you sit down to a mountain of spaghetti. This is how most runners "carb load." And it's almost entirely useless.

Here's why. Your muscles can only store about 400-600g of glycogen. Filling those stores takes time — glycogen synthesis happens at a rate of roughly 5-7% per hour. One big pasta dinner adds maybe 150-200g of carbs to your system. Even if your body processed all of it perfectly, you're only topping up a fraction of your glycogen stores. And the bloating and GI distress from overeating the night before a race? That's actively working against you.

What actually works is a 2-3 day carb loading protocol: eating 8-12g of carbs per kilogram of body weight per day for 48-72 hours before your race. For a 70kg runner, that's 560-840g of carbs per day — spread across all meals over multiple days, not crammed into one dinner.

The evidence is clear. A 2026 meta-analysis in Sports Medicine found that multi-day carb loading protocols improved endurance performance by 2-3%, while single-meal loading showed no significant benefit.

This one refuses to die. The logic: if you run without eating, your body has to burn fat for fuel. More fat burning = more weight loss = faster runner. Right?

Not exactly. While it's true that fasted exercise increases fat oxidation during that specific session, research consistently shows that this doesn't translate to greater fat loss over time. A 2026 study in the Journal of the International Society of Sports Nutrition found no difference in body composition between fasted and fed training groups over 4 weeks — despite identical calorie intake and training volume.

What fasted running does do: it increases cortisol, impairs high-intensity performance, accelerates muscle protein breakdown, and makes your workout feel harder for the same pace. For easy recovery runs under 60 minutes, running fasted is fine. For any quality session — intervals, tempo, long run — you're sabotaging the workout.

The nuance: there is legitimate research on "train low, compete high" strategies where athletes occasionally train with low glycogen to enhance mitochondrial adaptation. But this is a periodized strategy used by elite athletes under professional guidance — not a daily habit for recreational runners trying to lose 5 pounds.

The "anabolic window" — the idea that you must consume protein within 30 minutes of exercise or lose your gains — is one of the most persistent myths in sports nutrition. And the supplement industry loves it, because it sells a lot of protein powder.

The reality: the post-exercise "window" for protein synthesis is much wider than 30 minutes. A 2026 meta-analysis in the Journal of the International Society of Sports Nutrition found that total daily protein intake mattered far more than timing. Eating a normal meal with 20-40g of protein within 2 hours of training is equally effective as slamming a shake in the parking lot.

For runners specifically, the bigger issue isn't protein timing — it's carb timing. Glycogen resynthesis is most efficient in the first 30-60 minutes post-exercise. If you're going to obsess about timing, obsess about carbs, not protein.

Gel companies want you to believe that every run requires their product. Some runners carry gels for a 45-minute easy run. This is unnecessary and expensive.

Your body stores enough glycogen for roughly 90 minutes of moderate-intensity running. For runs under 90 minutes, you don't need external carbs — assuming you ate normally that day. Water is sufficient.

Gels become necessary for: long runs over 90 minutes, races (half marathon and up), and back-to-back sessions where glycogen may already be depleted. For everything else, save your money and your GI tract.

Exception: if you're training your gut to tolerate race-day fueling, it makes sense to practice with gels during some shorter long runs. But this is training your gut — not fueling the run.

The fitness industry has convinced everyone that more protein is always better. Runners are bombarded with protein-fortified everything: bars, shakes, recovery drinks, even protein water. But for endurance athletes, the real performance limiter isn't protein — it's carbohydrates.

The International Society of Sports Nutrition recommends 1.2-1.6g of protein per kg per day for endurance athletes. For a 70kg runner, that's 84-112g — easily achievable through normal food. Meanwhile, most recreational runners chronically undereat carbs, which are the primary fuel for running and the substrate for glycogen recovery.

If you're choosing between a chicken breast and a bowl of rice after your long run, choose the rice. You can get your protein at dinner. But your glycogen stores need carbs now.

For decades, sports drink companies pushed the message that thirst is a poor indicator of hydration — and that by the time you're thirsty, you're already dehydrated. This led to the over-drinking epidemic that actually caused more problems than it solved.

Exercise-associated hyponatremia (dangerously low blood sodium from drinking too much water) hospitalizes runners every major marathon. It's more common — and more dangerous — than dehydration in recreational runners. A 2026 study in the Clinical Journal of Sport Medicine found that hyponatremia affected up to 13% of marathon finishers, while clinically significant dehydration was rare.

The current evidence-based guidance: drink to thirst. Your body has evolved a highly sensitive mechanism for detecting fluid needs. Trust it. For long runs and races, carry fluid and drink when thirsty — but don't force yourself to drink on a schedule.

This is the biggest myth of all — and the one that training plan apps inadvertently reinforce. When you track calories in MyFitnessPal or any standard nutrition app, you get one daily target. It doesn't change on hard days, easy days, or rest days.

But your body's energy needs swing wildly depending on what you're doing. A rest day might require 2,000 calories. A long run day might require 3,200. Eating 2,600 every day means you're underfueled when it matters and overfueled when it doesn't.

Periodized nutrition — adjusting daily intake to match training load — is the standard practice among elite endurance athletes. It's not complicated, but it requires your nutrition to talk to your training plan. That's exactly what MAVR does.