There is much debate, both among runners and sports scientists, about whether running on an empty stomach is beneficial. The current science suggests that rather than doing the same thing every time you run, your decision should be based on the specific goals you set for each morning workout.
Fasting for Fat Loss
One reason runners and other athletes choose to exercise in a fasted state is to burn more fat. Exercising when glycogen stores are low, as is the case when you just wake up in the morning, forces the body to burn more fat to fuel your activity. However, the Strength and Conditioning Journal reviewed the applicable research and concluded that fat oxidation was only increased as a result of fasting when intensity levels were kept low and the exercise session was long — in one case, the fat-burning benefits only began at the 90-minute mark.
So, if fat loss is a goal, then doing some long, slow distance runs on an empty stomach during your off-season could be an effective strategy. It's important, however, that you keep your effort at a level that allows you to carry on a conversation, or at or below 65 percent of VO2Max. If your glycogen stores are at zero and you exercise at an intensity requiring energy faster than your body can oxidize fat, your body will automatically turn to muscle as the next source of energy. Everyone will agree that burning muscle is undesirable, regardless of what kind of runner you are.
Boosting Performance on an Empty Stomach
The other reason to run on an empty stomach is to improve performance. The thinking goes that if an athlete trains properly in the fasted state, their body will "learn" to burn fat as the preferred fuel source. At least one study from the National Institutes of Health has shown this to be true: test subjects who exercised on an empty stomach four times per week for six weeks showed an increase in the breakdown of fat stores within the muscles. However, it should be noted that the exercise intensity at which that happened was a relatively low 65 percent of VO2Max.
Perhaps the best reason to occasionally run on an empty stomach is that it can simulate the way your body feels in the late stages of a long race. By experiencing what running on empty feels like, you can be mentally ready to push through the wall, and you can practice different fueling strategies to see what your body responds to best.
When It's Best to Eat Breakfast
In most cases, eating before a morning workout will result in a higher quality training session. What you eat, when and how much can affect your workout, though. If you're going to eat a full breakfast, you should do so at least 90 minutes before you run. If you want to get out the door earlier, then opt for a low-fiber, easily digestible, carboyhdrate-rich snack, such as a banana or a green smoothie. (Check out these post-workout smoothie recipes).
Rashelle Brown is a freelance writer primarily covering topics of health, wellness and fitness. Her work has appeared in IDEA Fitness Journal, and she contributes regularly to Livestrong.com, Active.com and the PBS website Nextavenue.org. She is also the founder of Well Curated Life, a website dedicated to helping individuals live healthy, happy lives.