Training on Empty Stomach?

Sean Callahan, Tony Horton, and I at Santa Monica Muscle Beach

NYTimes released an article last month on the benefits of exercising before breakfast – training on empty stomach is proven to be effective in burning bodyfat. However, the article did make a point that training on empty will not improve your performance during a workout. So the main question is, if you’re somewhat in shape and your main goal is to improve sports performance, agility, strength and muscle size, would it be bad to train on empty?

It is just a common sense that you will feel more like training if you eat a small snack beforehand. It’s important to enjoy your training, because you’re not likely to keep doing an activity that you find unpleasant. I wake up with Shakeology and 1 scoop of whey protein about 45-60min before starting my workout. And about 10-15 min before workout, I would start drinking a pre-workout supplement. If you do not have enough time for Shakeology or anything heavy, and just want something light and quick, any preworkout supplement, skim milk or an apple would do the trick. Avoid concentrated sugars which cause a spike in your blood sugar – a candy bar or honey are no-nos – or eating so much that you feel full and uncomfortable. Eat something small in volume and easily digested.

The main reason for a pre-workout snack, however, is to supply your brain with the energy it requires to function properly – and to avoid cannibalizing your muscles.All the different tissues of the body, including your muscles, use glucose, blood sugar, for energy. Your brain, however, relies on glucose for energy almost exclusively. If your blood glucose level falls, the brain cannot function properly. The result is usually inability to concentrate, lethargy and confusion. For this reason, the body is programmed to maintain your blood glucose level no matter what the cost.

Most of the energy for a training session, weights or aerobics, come from the glycogen stored in your muscles. The glycogen comes from what you have eaten over the last several days, not your last meal. It takes a day or two to restore the glycogen to depleted muscles. About 200 grams of glycogen can be stored in your muscles. Muscle glycogen, however, is no help to your brain; it can’t get out of the muscles to raise your blood sugar. So where does the glucose for your brain come from?

First, it comes from the glucose contained in your circulating blood. This, however, is only about 20 grams and doesn’t last long. Next, it comes from the breakdown of glycogen to glucose in the liver; that’s about 70 grams. The glucose in your circulating blood and that stored in your liver, is enough to tide your brain over during the night, but that’s about it. When you get up in the morning the body must look elsewhere to supply glucose to your brain. Unfortunately, if you don’t eat, the source of supply is body protein — not the fat stored on your body.

As you probably know, extra calories from any source, carbohydrate, protein or fat, are stored as fat. “The catch,” is that this is a one-way street.” Fat cannot be used to form glucose. Under normal circumstances, body fat can’t supply the needs of the brain. (After about two days of starvation body fat can provide energy to the brain, but that’s clearly not acceptable for our purposes.)

After blood glucose and liver glycogen are used up, the body turns not to fat tissue, but to protein to maintain the blood glucose level. The mechanism is called gluconeogenesis, the manufacture of new glucose. Your liver does the job. It strips the nitrogen from body protein to form glucose. In other words, protein from skeletal muscles and other body structures is used to maintain your blood glucose level.

Dr. Lawrence Lamb, M.D. and fitness expect in Sports Performance, summed it up like this: “In the morning, after an overnight fast, your body has already switched to converting amino acids to glucose. That is one reason why some carbohydrate to support your blood sugar level early in the morning is important. That can help conserve the cell protein, such as found in your muscles.”

So, training in the morning on empty, without eating, is a bad idea. The result is exactly the opposite of that desired. Rather than encourage the burning of fat, if forces your body to burn hard-earned muscle.To the best of my knowledge, Dr. Lamb’s comments are still state-of-the-art. I have yet to hear any authoritative opinion to the contrary. Until I do, I plan to continue eating a pre-workout snack.

I’ve had many questions on this topic. I hope this clears up the confusion about eating a pre-workout snack. At the end of the day, to eat or to not eat before exercising depends a lot on your fitness level and goals.




2 Responses to Training on Empty Stomach?

  • Thanks for the information. I should be able to put this info to good use in the near future.

    Whole grains contain large amounts of plant fiber, is something that can be digested fibers, including cellulose, hemicelluloses, lignin and other substances.

  • Thanks. I wondered about that. I eat about half a protein bar or drink a half cup of juice to support my blood sugar before or during my workout. I am diabetic so my blood sugar will rise initially when I start to move and make me sluggish, but it will get used up a few minutes into my workout. So I take a glucose tablet or half a bottle of apple juice to make sure my blood sugar remains high enough to keep me strong.
    It’s a balancing act and I listen to my body to be safe.