Carbo Loading

I have witnessed many endurance athletes over the years who have failed to successfully carbohydrate loading prior to their big event. To help you avoid the common pitfalls I would like to share with you the following background on the technique and tips:

What is carbohydrate loading and Who does it benefit?

It is a strategy involving changes to training and nutrition in order to maximize muscle glycogen (carbohydrate) stores prior to endurance competition.

It is likely to benefit anyone exercising continuously at a moderate to high intensity for 90 minutes or longer . Examples include sports such as cycling, marathon running, longer distance triathlon, cross-country skiing and endurance swimming. Shorter-term exercise is unlikely to benefit as the body’s usual carbohydrate stores are adequate. In team sports where games are played every 3-4 days carbohydrate loading is generally not practical to achieve as it may not be possible to achieve a full carbohydrate loading protocol within the weekly schedule of training and games.


The technique dates back to the late 1960’s . Originally it involved a 3-4 day ‘depletion phase’ of hard training plus a low carbohydrate diet. This “depletion” phase was considered necessary in order to stimulate the enzyme glycogen synthase. This “depletion” phase was then followed immediately by a 3-4 day ‘loading phase’ involving rest combined with a high carbohydrate diet. The combination of the two phases was shown to boost muscle carbohydrate stores beyond their usual resting levels. Studies since this time have clearly demonstrated that the “depletion” phase is not necessary to achieve successful carbohydrate loading.

Top 5 mistakes made when carbohydrate loading

Failure to adequately taper. If an athlete finds it difficult to significantly back off training and taper for 1-4 days before competition carbohydrate loading will be compromised.

Failure to eat enough carbohydrate. If the athlete does not have a good understanding of the amount of food required to carbohydrate load I strongly suggest they work with a sports dietitian/nutritionist . Using a carbohydrate counter can be useful.

Not cutting back on fibre and fat. In order to consume the necessary amount of carbohydrate, it is necessary to cut back on fibre and make use of compact sources of carbohydrate such as sugar, sports drinks, FLY, jam, honey, maple syrup, jelly, ‘dried’ fruit and tinned fruit. Athletes who include too many high fibre foods in their carbohydrate loading menu are likely to suffer stomach upset or find that the food is simply too bulky to consume.

Fear of weight gain. Body mass will usually increase by approximately 1-2% of your normal weight, when effectively carbo loading. The extra weight is due to extra muscle glycogen and water. Weight gain fears prevent some athletes from carbohydrate loading adequately.
Binge Eating. Some athletes see Carbo loading as an excuse to eat anything they want in unlimited quantity. Consuming too many high fat foods makes it difficult to consume the amount of carbohydrate necessary. It may also result in body fat increase. A high-carbohydrate, low-fat approach is fundamental to the success of carbohydrate loading.

How much will carbohydrate loading improve my performance?

Muscle glycogen levels are normally in the range of 100-120 mmol/kg ww (wet weight). Carbohydrate loading enables muscle glycogen levels to be increased to around 150-200 mmol/kg ww. This extra supply of carbohydrate allows athletes to exercise at their optimal pace for a longer time. It is estimated that carbohydrate loading can improve performance over a set distance by 2-3%.

What does an effective carbohydrate loading diet look like?

The following diet is suitable for a 70kg athlete aiming to carbohydrate load:


3 cups of low-fibre cereal with 11/2 cups of reduced fat liquid
1 medium banana
250ml Orange juice or sport drink


toasted white bagel with honey or jam or maple syrup.
500ml sport drink plus a scoop of FLY


2 sandwiches (4 slices of white bread) with filling as desired
200g tub of low-fat fruit yoghurt
375ml of sport drink.


banana smoothie made with low-fat rice milk


1 cup of pasta sauce with 2 cups of cooked pasta
3 slices of garlic bread
1 glass of sport drink with 1 scoop FLY

Late Snack

toasted muffin and jam/honey/maple syrup
250 ml sport drink

This sample plan provides ~ 14,800 kJ, 630 g carbohydrate, 125 g protein and 60 g fat.

Are there any difference in the effects of carbohydrate loading in males compared to females?

Further research needs to be conducted on females. Most studies of glycogen storage have been conducted on male athletes. Some studies suggest that females may be less responsive to carbohydrate loading, especially during the follicular phase of the menstrual cycle. This appears to be, at least partly, because they have difficulty consuming the larger amounts of carbohydrate required for a complete CHO load. This problem may be solved in part by using highly concentrated liquid carbohydrate sources.

Douglas W. Stoddard MD, M Sport Med, Dip Sport Med, ES
Medical Director-Sports & Exercise Medicine Institute (SEMI)
Medical Director-e load Sport Nutrition