For Ironman and Epic nutrition, learning to burn fat is a key strategy to reduce gastric issues and optimise performance.
The body can sustain the absorption of around 1100 kilojoules per hour. At higher rates you gastric system is highly likely to fail, usually around 7 hours of racing. The usual signs are the dreaded bonk, bloating and cramps.
In an Ironman you will burn between 3000 and 3800 Kilojoules per hour, 60% of the fuel you rely on will be your own body fat.
Ironman athletes commonly train up to seven hours on a sugar intensive fuels, never going to the stage where our gastric system starts to fail.
If you don’t teach our body to burn fat you will have a heavy reliance on external fuel which our gastric system can’t support in the later stages. This is unlikely to occur in races less than 7 hours.
Complex sugars are the best fuel for racing with intensity and the best choice in the ironman race, however you can reduce the levels required to the optimal sustainable absorption of around 65 grams per hour.
To train the body to burn fat you will need to do some training without the usual sugar based fuels. If you have always trained with sports drinks, gels and sports bars, take care as it takes time, doing a three hour session first time out is unlikely to end well. Start with shorter sessions and extend over time. Then move to 2 hours water then boiled new potatoes (with salt) or oat meal bars. Avoid wheat and refined grains and they increase insulin production which in turn reduces fat burning. Those who do no sugar rides frequently can safely do 5 hours on no sugar fuels. It is important to take on electrolytes, either using no sugar electrolyte drinks or salt tablets.
As a general rule I apply the following to adapt and maintain a fat burning capability:
- Sugar for any training up to 90 minutes, generally water only
- No sugar fuels for any training session where the majority is at zone 2 or below, up to 5 hours. Fuels can include boiled salted new potatoes with paprika, sweet potato as a paste or oats based bars.
- Sugar based fuel limited to 65 grams per hour for sessions above zone 2 over 90 minute.
- Swills of sugar drink for high intensity sessions (race pace) up to 90 minutes.
It is important to take on sufficient electrolytes, usually found in sports drinks and gels. Required levels can be established through sweat tests, commonly replacement levels of 500mg to 700mg per hour.