Is Carb Loading a Myth? What the 2026 Research Says

Quick Answer 

No, carb loading is not a myth. The 2026 commentary behind the headlines was not a new performance study. It reviewed 14 existing studies, only 2 of which were double blind placebo controlled trials, and most tested carb loading with no fuel taken during exercise at all. Those studies asked whether topping up an already high glycogen store adds performance, which is a very different question to the one most age group triathletes need answered. When researchers followed 27 female triathletes racing the 2024 IRONMAN World Championships, only 26% met carb loading guidelines and the group averaged just 6.4 grams of carbohydrate per kilo. For most age groupers, carb loading is rarely being done properly in the first place.

A comment landed on one of my posts recently. Four words. "Carb loading is a myth."

My first instinct was to argue. My second was to ask what they actually meant by it. And their answer was, technically, correct physiology.

There is a real paper behind that comment, and the headlines have run a very long way with it. Take them at face value and you might walk into your next 70.3 having eaten a completely normal Saturday dinner, then wonder why the back half of the run fell apart.

What Does the New Research Actually Say About Carb Loading? 

The paper causing the noise was published in June 2026 in the International Journal of Sport Nutrition and Exercise Metabolism (Areta et al., 2026)

Start with what kind of paper it is. It is a commentary, not a carb loading performance study. Nobody was put on a bike and made to ride 180 kilometres. No new data was collected. The authors went back through six decades of existing research and offered their insights, which is a genuinely useful exercise.

They screened 10,422 papers, filtering down to studies with an endurance performance test longer than 90 minutes, comparing a "normal" carbohydrate intake of 4 to 6 grams per kilo against a loading intake above 7 grams per kilo, over at least 24 hours.

That left 14 studies. Sixty years of research, and the evidence base here is 14 papers.

Why Only 2 of Those 14 Studies Really Count

Only 2 of the 14 were double blind placebo controlled trials (where neither the athlete nor the researcher knows which arm of the study they are in, the gold standard for removing bias).

That matters. If you know you have loaded and you believe you are sitting on a full fuel tank, you might simply ride harder. That is the placebo effect and it is very real. Blinding carbohydrate is also genuinely hard. It is not easy to sneak 600 grams of carbohydrate past someone who has to sit there and eat it (apparently a nasogastric tube is an option, but I will pass).

Three more numbers change how you read this:

• Only 4 of the 14 studies gave athletes any carbohydrate during the performance test
• That means 10 studies, 71% of this evidence base, tested carb loading with zero fuel on board
• 7 of those also tested athletes fasted. No breakfast. No pre race meal

The 4 that did fuel their athletes gave 60 to 70 grams of carbohydrate an hour, ambitious for the time but well below where the sport sits now. I broke that trend down in Episode 53, Why Aiming for 120g of Carbs Per Hour Is a Mistake.

The 2 double blind studies are where the myth claim comes from, and neither found a significant performance benefit. But one fed its cyclists 9 grams per kilo against a 6 gram control (Burke et al., 2000, Journal of Applied Physiology), arguably underdosed for a loading protocol. The other was primarily a creatine study, with loading sitting alongside creatine as one variable across three groups (Tomcik et al., 2018, Medicine & Science in Sports & Exercise). It was never designed as a carb loading study, and its own authors flagged that the design may have masked the effect.

Both were in well trained male cyclists. Both were in a lab. That is not a case closed. That is a case barely opened.

Is Carb Loading a Myth, or Is Your Fuel Tank Just Not Full?

Here is where that original comment was correct. Your muscles store a finite amount of glycogen (the storage form of carbohydrate in your muscles). Once those stores are full, more carbohydrate will not keep pushing them higher. There is a ceiling. More is not better.

But "a ceiling exists" and "your tank is already full" are two completely different statements.

When researchers fed athletes properly, glycogen moved. A 2026 dose response study gave endurance trained athletes 6, 8 and 10 grams per kilo and found a linear relationship between intake and muscle glycogen, with 10 grams per kilo producing the highest concentrations (Jones et al., 2026, Scandinavian Journal of Medicine & Science in Sports). Not a myth. A dose response.

Some athletes genuinely are at the ceiling. For 6 years I was one of the dietitians looking after the Australian elite triathlon team, and I never wrote Matt Hauser a carb loading plan. Not once! He did not need one, because he already ate at loading levels every normal training day, so tapering was enough. You can hear him on Episode 227.

The research is arguing about getting from 90% full to properly full. Most age groupers are still filling the bottom half of the tank.

What Female Triathletes Actually Ate Before World Champs

This is the study that matters far more to you than the commentary does.

Researchers followed 27 female triathletes competing at the 2024 IRONMAN World Championships, using 48 hour food diaries and interviews before and after the race (Fortis et al., 2026, European Journal of Sport Science). Not lab rats. Real age group athletes in the real world.

These women qualified for World Champs. They trained for years to get there. They flew across the world. Nobody cares about a race more than that.

Only 26% of them hit carb loading guidelines of 8 to 12 grams per kilo. The group average was 6.4 grams per kilo.

Read that again, because it is the whole point. 6.4 grams per kilo is the control group in the very studies everyone is quoting. These women were eating the amount that research calls "not carb loading" on World Champs eve, while genuinely believing they were loading. For a 65 kilo triathlete, the gap between 6.4 and 10 grams per kilo is about 234 grams of carbohydrate. That is roughly 5 cups of cooked pasta you did not eat!

The athletes who ate more carbohydrate also raced faster, and that relationship was statistically significant. Correlation is not causation, and the women eating more may simply have been more organised across the board. But it points the same direction as everything else I see. You have an elite athlete mindset. You spend money on the bike, the watch, the coach and the carbon fibre shoes. And then you fuel like a complete beginner. I say that with love, as someone trying to help.

Why Carb Loading Is More Than One Number

Here is the second problem with applying this research to yourself, and I don't think enough people are talking about it.

The commentary looks at one parameter: grams of carbohydrate. But loading done properly is not carbohydrate alone. It is 5 numbers. Your carbohydrate, your protein, your fat, your fibre and your total energy across your loading days.

Nail the carbohydrate and get the other 4 wrong, and you will feel bloated, heavy and flat on race morning. Then you will quite reasonably decide carb loading does not work for you. That is not loading failing. That is a plan built from one number instead of 5. Done properly, with the right food choices, this does not have to feel awful.

How Should You Carb Load for Your Next Race?

Nothing here is a reason to skip it. Think about it as risk versus reward. You have spent months training, plus money on the bike, the coach, the entry and the flights. Loading is a couple of days of eating deliberately. Safe, cheap by comparison and completely reversible. One of the commentary's own authors has said publicly that if it might work and it is not hard to do, you would be silly not to do it until we know more.

A few things should change how you do it:

• Start earlier than the night before. Guidelines sit at 8 to 12 grams per kilo for 24 to 48 hours before an event over 90 minutes. One big bowl of pasta on Saturday night is not carb loading
• Look at a normal training day first. If your everyday carbohydrate is too low, no amount of race week pasta will rescue you
• Watch your fibre. High fibre plus a nervous gut on race morning is a combination nobody enjoys
• Stick with familiar foods and don't do anything weird. Never try anything new on race day
• Practise it well before race week. If your first attempt is 2 days out from Cairns, you have made your race the experiment
• If you are a female athlete, understand your cycle. Hitting your numbers matters even more

 If your race is under 90 minutes, then a normal high carbohydrate day and a solid pre race meal will do. If you are racing 70.3 or Ironman distance, then a structured 24 to 48 hour load is worth doing properly. For where your during race fuelling sits alongside it, I covered that in Carbs Per Hour for Triathlon.

FAQ

Q: Is carb loading a myth?

A: No. A 2026 commentary reviewing 14 studies found limited double blind evidence that loading improves performance, but only 2 of those studies were double blinded and most tested athletes with no fuel during exercise. Separate research shows a clear dose response between carbohydrate intake and muscle glycogen up to 10 grams per kilo.

Q: How many grams of carbs per kilo do you need to carb load?

A: Guidelines sit at 8 to 12 grams of carbohydrate per kilogram of body mass per day. For a 65 kilo athlete that is 520 to 780 grams a day, far more food than most people picture. Research at the 2024 IRONMAN World Championships found female age groupers averaged just 6.4 grams per kilo.

Q: How many days before a race should you carb load?

A: For events longer than 90 minutes, 24 to 48 hours of high carbohydrate intake alongside a training taper is the standard protocol. Starting the night before is too late to meaningfully change your glycogen stores, and far more likely to leave you feeling heavy on race morning.

Q: Does carb loading make you gain weight?

A: You will hold some extra water, because glycogen is stored with water in the muscle. A 2026 dose response study of intakes from 6 to 10 grams per kilo found no detectable effect on body mass. Any small change is fuel, not fat, and it disappears as you use it during the race. 

Q: Do female athletes need to carb load differently?

A: Female athletes need to pay closer attention to hitting their numbers, and menstrual cycle phase can influence how the body responds. Almost all of the older carb loading research was conducted in men, so this is an area where the evidence is still developing.

Bottom Line

Is carb loading a myth? No. But the way a lot of age groupers do it might be. 

The research is arguing about the top of the fuel tank. Most age group triathletes are still trying to fill the bottom half. And loading was never just a carbohydrate number anyway, in foods you already know work, in a body that is uniquely yours. There is no one size fits all here. You are your own experiment. 

If reading this made you realise your loading has been a big bowl of pasta and a bit of hope, don't stress! It is a very fixable problem once you know your actual numbers.

My Carb Loading Masterclass lays the whole thing out in plain language, with a planner and a calculator that does the hard maths for you. It gives you all 5 of your numbers, not just one, plus how to apply it as a female athlete across your cycle.