What does training low mean for athletes?

A trend among endurance athletes is to intentionally train with low glycogen (sugar-based energy) stores. Your body naturally turns to available blood sugar and then glycogen stores of energy during the early phase of exercise. Once that's burned, the body starts to force fat metabolism, the next available source of energy. So if glycogen storage is low to begin with, the theory is that you will quickly begin to burn fat as your energy supply. Hence, the term training low. 

How is this accomplished? Remember that various foods supply glucose (sugar), especially carbohydrates.  So if your carbohydrate intake is low, you end up with low glycogen stores.

To get the process started begin to taper your intake of carbohydrates for a few days during training, while increasing (healthy) fat intake. Embracing this kind of a diet requires a health professional to guide and monitor you, since very low carbohydrate diets can present certain health challenges. Always check with your physician before beginning an exercise program or a new dietary approach.