Louise Burke published an interesting overview of low carb nutrition for endurance sports in the Journal of Physiology. Burke outlines how a 5-10 day low carb diet leads to a significant increase in maximum fat burning. Their review suggests that short-term, low-carb periods may be useful to up-regulate fat metabolism adjustments, while periods of higher carbohydrate availability could be used to maintain exercise quality and high-intensity performance. Burke's rating refers to Olympic sports (with the most duration of 1 to 5 minutes) and not to performances of several hours.
This "periodic low carb diet" is the approach we take with the Vivere180 Kick Start program - the 7 day program to maximize fat metabolism adaptation over a short period of time, followed by our follow up program to maintain the important metabolic adjustments. You can read the abstract here