The pros and cons of carbo-loading

Carbo-loading principles
Carbo-loading for the marathon was pioneered in the UK in the 1970s by running legend Ron Hill, who experimented with ‘the diet’ as it was known then. Ron Hill won a gold medal for the marathon in the 1970 Commonwealth Games, winning in two hours and nine minutes; a phenomenal performance which would stand up against any championship marathon time four decades on. Crediting part of his success to his nutritional preparation, ‘the diet’ centres around two distinct phases, namely depletion and loading.

• The depletion phase. This phase involves eating minimal or nil carbohydrate, keeping hydration levels high and stocking up on protein. Effectively, your carbohydrate fuel tank runs low to empty – you become depleted when running.

• The loading phase. Immediately following the depletion phase, you switch to the loading phase. This is effectively the reverse of depletion, whereby protein intake is reduced and carbohydrate is increased significantly. Hydration is still maintained at a high level.

• The end result. The effect of these is that your carbohydrate fuel tanks in your liver and muscles super-compensate for the depletion phase and maximise their supplies, so that you start your race by running with a completely full tank.

Carbo-loading advocates describe going into races bursting with running confidence and claim the following benefits:

• Boundless running energy
• Never hitting the dreaded ‘wall’
• More running energy in the final few testing miles

Carbo-loading detractors advise that a modified carbo-loading system is just as effective to runners, particularly because of the side effects that can be experienced, which can include:

• Nausea
• Fatigue
• Excessive hunger
• Reduced immune system function
• Irritability
• Subsequent bloating
• Poor pre-race fuel stocks

Clearly, carbo-loading is not to be taken lightly and can be approached in three different ways; full blown, modified and basic. So, if you want to give it a try for your next long-distance running event, use our comparison below and see which system is best for you.

Carbo-loading – the comparison
Assuming that your race is on a Sunday, start the programme with a run of approximately ten miles on the preceding Sunday, at the same time as your planned race but at a much slower and easier pace. The remainder of your training during this final week tapers towards the big day and the focus is on your nutrition and hydration.

• Full blown carbo-loading system

Description: Nil carbohydrate during depletion phase.

Depletion phase – Sunday to Thursday 12.00 (noon)
1. Starting after your last ten mile run, completely eliminate any form of carbohydrate.
2. Eat plenty of protein, salads, cheese etc. and keep hydration levels very high.

Loading phase – Thursday 12.00 to Sunday morning
1. On Thursday morning, complete a short run of approx four miles.
2. Post run, immediately start eating large quantities of carbohydrate.
3. Focus on complex forms, for example: pasta, whole-grains and rice.
4. Keep hydration high and include small quantities of protein.

Notes: Eat a normal pre-race breakfast, by now you should be feeling very full.

Pros: Could result in a personal best run
Cons: High risk, hard to adhere to, and end result could be low fuel stocks if insufficient fuel consumed during loading phase.

• Modified carbo-loading system

Description: Small quantities of carbohydrate eaten during depletion phase.

Depletion phase – Sunday to Thursday 12.00 (noon)
Similar to the full-blown system but, include a small amount of carbohydrate, for example: breakfast cereal each morning.

Loading phase – Thursday 12.00 to Sunday morning
Exactly the same as for the full-blown system:

1. On Thursday morning, complete a short run of approx four miles.
2. Post run, immediately start eating large quantities of carbohydrate.
3. Focus on complex forms, for example: pasta, whole-grains and rice
4. Keep hydration high and include small quantities of protein.

Notes: eat a normal pre-race breakfast, by now you should be feeling very full.

Pros: Lower risk, the ability to super-compensate may be slightly less but should still result in good carbohydrate stocks.
Cons: May not maximise fuel stores as well as the full-blown system.

• Basic carbo-loading system

Description: Carbohydrate allowed in slightly reduced quantities from normal intake.

Depletion phase – Sunday to Thursday 12.00 (noon)
After your ten mile run, decrease your carbohydrate intake slightly.

Loading phase – Thursday 12.00 to Sunday morning
In the last three days before your race, increase your carbohydrate intake.

Notes: Prepare exactly as you would for any race.

Pros: No risks or side effects and easy to adhere to.
Cons: Does not invoke the super-compensation technique so fuel stores are unlikely to be at absolute optimum.

Advanced methods of fuelling your running fitness
For the novice marathon runner, the basic system is most suitable. You are learning the event and you can do without potential problems in the final week. However, as your experience grows, you may like to try more advanced methods of fuelling up. Clearly there are risks associated with the full-blown system and the possibility that your fuel stocks may not reach maximum if you fail to load sufficiently in the final days. However, if you get the timing right, the benefit of a completely full tank is certain to make the difference as your race progresses.

One solution is to try for the middle ground and experiment with the modified system for your next running event. The risk of experiencing any side effects is lessened, yet there are still significant benefits to enjoy. If you find that it works for you, you can then decide if you really want to go the whole hog and try the full-blown method or simply stick with the tried and tested running system that you know works for you.