100% money guarantee

Free delivery from €100

Carb loading: time to retire the depletion diet

Coureur assis à la table de sa cuisine la veille d'un marathon, devant des pâtes, du riz, du pain et une banane, avec son dossard 1034 du Marathon de la Mule sponsorisé par Mulebar

Grégoire Dandres |

In 1967, a Scandinavian team invented carbohydrate loading: three days emptying the muscles, then three days filling them up. You probably know this depletion diet, or the express version of loading, the big plate of pasta the night before. Research simplified the method long ago. It has also shifted the challenge from deprivation to quantity, because many runners simply don’t eat enough.

1967: empty the tank to fill it fuller

Glycogen is the form in which your muscles store carbohydrates. It’s a limited fuel, the one that runs out when the effort goes on. Jonas Bergström and his colleagues want to know whether what you eat can enlarge this tank.

The researchers compared three diets over the three days before exercise. Nine students then pedalled at 75% of their maximum capacity until exhaustion.

  • On a very low-carbohydrate diet, their muscles contained 0.63g of glycogen per 100g of muscle. They pedalled for 37 minutes.
  • On their usual diet, they had 1.75g of glycogen and lasted 114 minutes.
  • After three days of a high-carbohydrate diet, their stores reached 3.31g and they pedalled for 167 minutes.

In other words, in this experiment, the high-carbohydrate diet nearly doubled the measured stores compared with the usual diet. The students also lasted 53 minutes longer on the bike.

This gave birth to the Scandinavian depletion diet. A long session empties the muscles, three days with almost no carbohydrates follow, then three days of pasta and rice. The idea was that a starved muscle would store more. In practice, the deprivation phase comes at a high price. Sports nutritionist Kathleen Deegan lists fatigue, irritability, sessions impossible to finish and more injuries.

1981: the same fill-up, without the deprivation

Fourteen years later, Sherman, Costill and their colleagues compare three ways of preparing for a 20.9km race, in trained runners.

  • The depletion diet: three low-carbohydrate days followed by three high-carbohydrate days.
  • The version without deprivation replaces the low days with three days of ordinary eating.
  • The third preparation keeps ordinary eating for all six days. In all three cases, training tapers day after day, from 90 minutes down to 20 minutes.

The biopsies, small samples of muscle tissue, settle the question. Both loading methods fill the muscles about 30% more than ordinary eating, and almost equally. The deprivation phase brings nothing extra.

This study teaches a second, lesser-known lesson. Over 20.9km, finishing times were the same in all three cases: loading pays off over longer efforts.

2002: one day to fill up

In Australia, Vanessa Bussau and her colleagues shorten the protocol even further. Eight endurance athletes eat 10g of carbohydrates per kilo of body weight per day, at rest. After a single day, their glycogen has almost doubled. Two more days add nothing.

This work set today’s benchmark. The joint position statement of the American College of Sports Medicine and American and Canadian dietitians (2016) recommends 10 to 12g of carbohydrates per kilo per day, for 36 to 48 hours, before events lasting more than 90 minutes. My Running page sets the bar slightly lower, at 8 to 10g over the last 48 hours. The two benchmarks meet at 10g.

The 90-minute mark

Carbohydrate loading is for long efforts. According to the review by John Hawley and his colleagues (1997), beyond 90 minutes it can delay fatigue by up to 20%. Between 60 and 90 minutes, the effect is close to zero and your usual training diet is enough.

In road running, it can be worthwhile before a marathon, and sometimes before a half if you run for more than 90 minutes. My nutrition tips for the half marathon go through the preparation. For a 10km, your usual training diet is enough. The article on the importance of glycogen explains how this tank empties, and the one on hitting the wall in the marathon describes what happens when it runs dry.

In trail running, an ultra or a race like the SaintéLyon goes well beyond this threshold. On the bike, the Cycling page points out that glycogen burns away on rides of two to six hours. The 1967 study was, in fact, carried out on a laboratory bike. In triathlon, starting with low stores tops the list of mistakes on the Triathlon page. Loading matters first and foremost for the 70.3, or half Ironman, and the Ironman.

The pasta plate doesn’t add up

In 2009, a British team asked 257 London Marathon runners, with an average finishing time of 4h34, what they had eaten the day before (Atkinson et al., 2011). Of these, 68% said they followed a high-carbohydrate diet. The group average came to 5g per kilo of body weight.

Those who exceeded 7g per kilo ran faster and held their pace better, with sex, body size and training taken into account. This is an observational study. It shows a link, not proof of cause and effect.

In a 24-hour race in Scotland, the same shortfall shows up: 4g per kilo per day on average over the two days before, and three runners out of sixteen at 5g or more (Kinrade and Galloway, 2021).

For a 70kg runner, 10g per kilo means 700g of carbohydrates per day. That’s about 2.4kg of cooked pasta.

Impossible to fit into two meals.

Fill the tank without overloading your stomach

First step: less fibre over the last two days. White bread, white rice, pasta, peeled fruit, compotes. A high-fibre meal is one of the factors behind digestive problems during exercise. People sensitive to FODMAPs, carbohydrates that ferment in the gut (found in onion, garlic, legumes and some fruits), do well to limit them on those days.

Second step: drink part of your carbohydrates. Monash University, which developed the FODMAP approach, publishes a sports dietitian’s guide on its website. The dietitian presents maltodextrin dissolved in water, a carbohydrate derived from starch, as an excellent option for carbohydrate loading. One serving of my energy drink in 500ml of water provides 35g of carbohydrates, from corn maltodextrin, sucrose (table sugar) and fructose. Xavier finds it “not too sweet” in his verified review of 11 September 2026, a detail that matters when you are getting through bottle after bottle.

Mulebar Citrus Energy Drink

To drink part of your load

Mulebar Citrus Energy Drink

35g of carbohydrates and 300mg of sodium per 40g serving, in 500ml of water. Available as a single serving or a 600g pouch, and in red berries flavour.

Discover the drink →

Third step: spread it out. Three meals and two or three snacks go down better than two giant plates. A banana energy compote provides 34g of carbohydrates and less than a gram of fibre. It slips in easily between two meals.

Women too, to the gram

In 1995, Mark Tarnopolsky and his colleagues observed that female endurance athletes did not store more glycogen when the share of carbohydrates on their plate rose to 75%, compared with the usual 55 to 60%. The men did. The team found the explanation in 2001: the women were eating less overall. When they eat more, their glycogen goes up.

That same year, in Australia, A. P. James’s team gave female and male athletes a dose based on their lean mass, that is, their weight without fat: 12g of carbohydrates per kilo of lean mass for three days. The women stored as much as the men, both before and after their periods. So count in grams per kilo, not as a share of your plate, and eat more overall during the loading days. My article on sports nutrition for women takes the subject further.

The dress rehearsal

Nothing new on race day, and the rule applies to the 48 hours before. Do a trial load before a long training run, with the foods, quantities and timings you plan to use. Then rate your digestive comfort from 0 to 10, as suggested in my complete guide to gut training, training your digestive system for exercise.

On race morning, keep your breakfast, light, two to three hours before the start. Liver glycogen, which keeps your blood sugar steady, does not seem to supercompensate the way muscle glycogen does (Gonzalez et al., 2016). Loading in the days before therefore does not replace this meal.

During the race, the gut training guide gives a benchmark of around 60g of carbohydrates per hour for efforts of two to three hours. The resealable cap on the energy gel lets you take it in three goes. For fluids, the article on marathon hydration sets out the plan before, during and after.

To put figures on your own race, the diagnostic app does the maths in two minutes, based on your sport, the length of your effort, your digestion and your tastes.

GET MY NUTRITION DIAGNOSIS →

In 1967, you had to starve your muscles to fill them up. Today, research asks for a simpler discipline, and one that makes sense: two days at the table, to reach the start line with a full tank.

Sources

Frequently asked questions

Is the Scandinavian depletion diet still useful before a marathon?

It adds nothing. In 1981, a study showed that three days of ordinary eating followed by three high-carbohydrate days fill the muscles as much as the version with deprivation.

The low-carbohydrate phase adds fatigue and irritability, without any extra glycogen.

How many carbohydrates per kilo for carbohydrate loading?

The 2016 joint recommendation is 10 to 12g of carbohydrates per kilo of body weight per day, for 36 to 48 hours, before an event lasting more than 90 minutes. My Running page sets 8 to 10g over the last 48 hours, and the two benchmarks meet at 10g.

For 70kg, 10g per kilo means 700g of carbohydrates per day.

How many days before a marathon should you start carbohydrate loading?

Two days are enough. In a 2002 Australian study, a single day at 10g per kilo, at rest, almost doubled muscle glycogen, and two more days added nothing.

Current recommendations specify 36 to 48 hours.

Is carbohydrate loading useful for a half marathon or a 10km?

It helps beyond 90 minutes of effort, where it can delay fatigue by up to 20% according to a 1997 review. Between 60 and 90 minutes, the effect is close to zero.

For a 10km, your usual training diet is enough; for a half, the question arises if you run for more than 90 minutes.

Should women adapt their carbohydrate loading?

They keep the same method and take care with the calculation. At an equal dose relative to lean mass, that is, weight without fat, women store as much glycogen as men (Australian study, 2001).

Simply increasing the share of carbohydrates on the plate is not enough if total intake is low. Count in grams per kilo and eat more during the loading days.

Why do you put on weight during carbohydrate loading?

Glycogen is stored with water, about 3g per gram of glycogen. Every extra 100g of glycogen therefore weighs about 400g on the scale.

This weight is a sign that the tank is filling up.

What should you eat during carbohydrate loading to avoid digestive problems?

Low-fibre carbohydrates over the last two days: white rice, pasta, white bread, peeled fruit, compotes. Drink part of your carbohydrates, for example an energy drink, and spread them over three meals and two or three snacks.

If you are sensitive to FODMAPs, carbohydrates that ferment in the gut, limit onion, garlic and legumes on those days. Test your menus before a long run.

Is a big plate of pasta the night before enough?

Rarely. For a 70kg runner, loading requires about 700g of carbohydrates per day, or 2.4kg of cooked pasta. It is the total for the day that counts.

At the 2009 London Marathon, runners who ate more than 7g of carbohydrates per kilo the day before ran faster, against an average of 5g. This is an observational study, which shows a link without proving the cause.

  • FREE DELIVERY

    From €100

  • LOVE IT ?

    Or your money back

  • FAST CUSTOMER SERVICE

    Reply within the day

  • 100% NATURAL INGREDIENTS

    No chemicals, no preservatives.

Join the Mulebar team and become a little mule