The good folks at coreperformance.com (a division of Athletes’ Performance) tackled this question: is it OK to train on an empty stomach?
According to AP’s director of performance nutrition, Amanda Carlson-Phillips, the answer is no. She says that if you attempt to train on an empty stomach, your performance will suffer when you work out at higher intensities and for longer durations.
But what if eating before a morning workout upsets your stomach? Carlson-Phillips advises experimenting with different breakfast menu items. Cereal and toast are easily digestible, and you can power up your toast with a peanut butter spread. Also, to insure proper hydration, opt for a sports drink or juice instead of milk, tea or coffee.
If you’re a carb and calorie counter, breakfast is best broken down with 30 to 60 grams of carbs and 10 to 20 grams of protein (check out Carlson-Phillips’ guide to the best protein sources). A balanced breakfast, Carlson-Phillips says, “will power your workout, increase strength and power, and burn more calories during your training session.”
So be sure to fuel up before firing up for a training session.