Carb Loading For Sport, Not For General Health

Carbohydrate loading is a concept that both athletes and the general pubic know of. This is largely due to the marketing of carbohydrate based products such as whole grains, sugary snack foods and sports drinks being the champion or elite sports performance, and in some part to information passed on via successful ex-elite athletes extolling the virtues of the dietary regimens that propelled them to the top of their sport. The concept of carb loading improving performance has been so successful that people think they need to carb load for all and any sports, be it before going to the gym, running a marathon or playing chess!

However, the continually evolving science of sports nutrition has moved on and the concept of carbohydrate loading, although still valid, is probably the most misunderstood term in sports nutrition. It is certainly not required for all sports and events. Conversely, some of the nutrition advice previously given to athletes to carb load including the consumption of toast and jam, jelly beans and sugary soft drinks seems obsolete, clearly we know these foods are full carbohydrate but they are devoid of other essential nutrients needed for elite performance and may even lead to the accumulation of excess body fat, which in itself may hamper performance. Consider for a moment that excess body fat creates inflammation, affects insulin signalling, alters appetite and disrupts hormone balance and you can begin to understand that eating too much carbohydrate for the wrong sports and events may make your performances worse.

Now, there is no doubt that carbohydrates are ergogenic and improve performance, there is too much research to suggest they do otherwise, however few athletes (except those who work with professional sports nutritionists) and very few of the general public would know when and how to carb load, which events or sports where is it applicable or how to do it with nutritious food.

What is carbohydrate loading?

Carbohydrate loading is a strategy employed by athletes that involves reducing training volume whilst simultaneously increasing the amounts of carbohydrates consumed in the days leading up to a game or event. The aim is to up regulate an enzyme called glycogen synthase (an enzyme that creates muscle fuel called glycogen) and cause the muscles to store higher than normal levels of glycogen. Muscle glycogen stores are normally about 100-120mmol/kg BW, but with carbohydrate loading they can reach 150-225mmol/kg BW.

Carbohydrate loading was originally developed in the 1960’s by Scandinavian researchers and involved a complicated 6-7 day period of a “depletion phase” – essentially a low carbohydrate diet – in conjunction with several hard training sessions. The aim of this phase was to deplete muscle glycogen stores and excite the enzyme glycogen synthase. Muscle glycogen stores could fall to as little as 25mmol/kg BW. This was then immediately followed by a 3-4 day “loading phase” where athletes would consume a very high carbohydrate diet (anywhere from 7-12g of carbohydrate per kg BW) whilst tapering exercise leading up to the event. However this approach to carbohydrate loading had its problems with athletes reporting muscle weakness, fatigue, anxiety and irritability.

Carbohydrate loading then evolved thanks to research out of Ball State University, Indiana, whereby the depletion phase was found to be unnecessary. Now athletes are advised that they don’t need to complete the “depletion phase” and only need to slowly taper exercise and to eat a high carbohydrate diet in the 3-4 days leading up to an event.

Consider an example below of a high carbohydrate diet from the Australian Institute of Sport (AIS) suitable for a 70kg athlete providing 630g of carbohydrate, 125g of protein and 60g of fat:

Breakfast: 3 cups of low-fibre breakfast cereal with 1½ cups of reduced fat milk, 1 medium banana, 250ml orange juice

Snack: toasted muffin with honey, 500ml sports drink

Lunch: 2 sandwiches (4 slices of bread) with filling as desired, 200g tub of low-fat fruit yoghurt, 375ml can of soft drink

Snack: banana smoothie made with low-fat milk, banana and honey, cereal bar

Dinner: 1 cup of pasta sauce with 2 cups of cooked pasta, 3 slices of garlic bread, 2 glasses of cordial

Late Snack: toasted muffin and jam, 500ml sports drink

The trouble with carbohydrate loading is that many people get it wrong – they use it as an excuse to eat anything they want, usually food laden with fat as well as sugar, but you can see from the example above that the food consumed should be low fibre, high glycemic load sugary, starchy foods – not fatty junk food. Herein lies another problem – this food is not very good for the teeth; it’s certainly not very good for blood sugar control and could lead to excess body fat accumulation if done too regularly, and it may lead to high triglycerides, gout or liver damage that have all been associated with consuming high amounts of fructose, high fructose corn syrup and sugar in general.

What do we need for performance?

In the example from the AIS above the foods, although high in carbohydrates, are also low in nutrition. Consider the diagram below of the kerbs’ cycle and electron transport chain (I can see you eyes glazing over here but bear with me). You don’t need to understand all the chemical reactions, just the fact that in order to turn all the carbohydrate in to energy you need a whole host of vitamins and minerals such as B vitamins, vitamin C, magnesium, CoQ10, copper, iron and sulphur.

Is carbohydrate loading necessary?

Carbohydrate loading is only really applicable for people exercising continuously at a moderate to high intensity for 90 minutes or longer. This immediately rules out gym goers and weekend warriors who play team sports on a Saturday, as most sports are not 90 minutes of continuous activity. Even in games such as football and rugby there are half time periods where refuelling can take place. It’s also not applicable to carbohydrate load for most team sports where there are regular games or multiple games per week. You would simply be in a continuous “loading phase” consuming way too much carbohydrate and less nutrient dense food from game to game.

Most people can complete a 5K and even a 10K run in less than 90 minutes, so it doesn’t seem applicable here either. With all of these sports it is still a good idea to consume carbohydrate based sports drinks during exercise and eat well balanced meals containing protein, fats and carbohydrates before and after exercise – you just don’t need to carbohydrate load.

How to prepare for exercise (including carbohydrate loading)

Carbohydrate loading should be done leading up to an important event such as a half marathon, marathon, triathlon or other endurance event where for 3-4 days prior to the event you can safely carbohydrate load as outlined by the AIS, and after having completed the event eat normally again. It might still be wise to consume some more nutrient dense carbohydrates foods such as tropical fruit, dried fruit and whole grains instead of foods such as jam, honey and muffins.

What seems more applicable for recreational athletes and those competing in team sports on a weekly basis is to get their sports nutrition right in the post training / post game window. Depending on what sources you read you have a 2-4 hour window after exercise to restock your muscle glycogen. It would be wise to consume higher carbohydrate based foods in this window; however it would also be pertinent to consume more nutrient dense food. Consuming fruit and vegetables in this time is a given, but also consuming some whole grains, starchy vegetables such as potato or sweet potato or some dried fruits such as figs, dates, raisins would also be useful. However it would be wiser to avoid fruit juice and soda drinks as these have been linked with diabetes, and avoid foods such as jams, jelly beans and sugary breakfast cereals as these are junk foods devoid of nutrition.

For the average gym goer wanting to lose weight there is no need to consume a higher carbohydrate diet – the whole point of most people going to the gym is to lose weight and eating a lower carbohydrate diet combined with resistance exercise has been shown to lead to good weight loss results.