Before I dive into this juicy topic, I want to make it clear that everyone reacts differently to various nutritional approaches, so the only true way to determine one's best nutritional strategy is through experimentation. In that same vein, the way in which one eats throughout an entire day is significantly more important than simply focusing on the hours before, during, after training.
Pre-workout nutrition is pretty simple. In my humble opinion entering a workout in a somewhat fasted state, will encourage optimal performance. I would advise not eating anything within 3 hours of a workout (especially if that workout is a fast paced met con). Everybody’s digestive system is slightly different and some people might be able to get away with wolfing down an entire meal 30 minutes before they do Fran (CrossFit WOD) for example.
Digestive diversity aside, I would still argue that everyone at least consider training in a fasted state for a couple of reasons. First of all, following the consumption of a somewhat large meal, gastric emptying occurs, meaning that a large percentage of one’s blood flow goes to the stomach to aid in the digestive processes as opposed to continuing to circulate throughout the body. Systematic blood flow does not occur in a state of gastric emptying, consequently exercising during this period of time will not lead to optimal performance nor an optimal hormonal response. That leads to my second reason for training on an empty stomach—it increases human growth hormone and the overall exercise induced anabolic response and consequently increases muscle growth (study on this theory http://www.springerlink.com/content/w8712615714k8150/). The increased anabolic response that occurs during and after “fasted” (not eating within 3+ hours) training is a compensatory response to the catabolism that occurs when training on an empty stomach.
So if you are not already training “empty” give it a try for a week or two and see how you look, feel and perform. For those craving (no pun intended) more regarding nutrition in conjunction with training my next post will cover post-workout eating.