Is Fat the Fuel of the Future?
by: Fiona Pelly
As we all know, both carbohydrate and fat can be used as fuel source during exercise. Up until now the emphasis has been on the performance enhancing effects of carbohydrate. However, it now appears that the role of fat has been underestimated. The latest research is showing that dietary fat may have more or a role in exercise performance than we have previously thought.
It appears that by manipulating our diet we can influence the proportion of fat and carbohydrate that is burnt. As we get fitter, we become more efficient at burning intra-muscular triglyceride (fat stored within the muscle). It seems that we can train the body to burn this fat more efficiently during exercise (ie fat adapt). This in turn will help to decrease our reliance on muscle glycogen. But remember most well trained individuals store enough glycogen for around 1.5 - 2 hours of continuous exercise, so most events will not benefit by fat adapting. It also appears that fat adapting is only of benefit for events over 3 hours (eg. Ironman, ultramarathon, 3 hour+ marathon).
You are still best training throughout the year on a high carbohydrate diet. In the week before your event begin with following a 3 day low carbohydrate, high fat regime, then carbohydrate load for the 3 days immediately prior to the event. Many of you will instantly say this reminds you of the 'old' method of carbo loading were the aim was to deplete the muscle of carbohydrate before the carbo load. Yes, this method is similar, however it is not necessary to train hard during the 'fat load' period. In fact it is still necessary to taper your training to ensure maximum fuel storage.
Another interesting finding is that fat ingested during exercise may also enhance performance for endurance activities. The only types of fat that seems to have this effect are known as medium chain triglycerides (MCT's). MCT's are absorbed and metabolised as quickly as glucose unlike most other fats. It appears that the best performancing enhancing effect occurs when the MCT's are combined with glucose. This is probably because the MCT's act as an addition fuel for the muscle.
MCT's are not found naturally in food and are presently sold to those with gastrointestinal problems who can't digest normal fat. They are also very expensive! It does appear that some companies in the US are manufacturing sports bars and gels containing MCT's and these are just starting to appear on the Australian market. The best solution would be to provide MCT's in a sports drink so that fluid requirements can be met at the same time, however it may be a long time before a palatable solution can be found!
- Carbohydrate is still the best fuel for training and competition
- For ultra-events, try fat loading followed by carbo loading (if possible, try in training first)
- Stick to sports drinks during the event. If you want to try MCT bars and gels remember to practice in training first and always consume plenty of fluid at the same time
Fiona Pelly, Cool Running Australia, 19.08.97