By Nick Nilsson

This is one of the most frequently-asked questions that I get! My approach is basically to base my recommendations on common sense (though after seeing all the other stuff on this site, you may not think that I have any! :)

While it IS true that it has been shown the training first thing in the morning on an empty stomach does increase fat burning (the commonly quoted stat is 300% greater), the problem is, you also increase the potential for burning up muscle at the same time.
The reason fat loss in increased at that time of day is due to blood sugar. Because your blood sugar is at it's very lowest, the theory is training at this time will force your body to rely more on bodyfat than on blood sugar to fuel activity.

This is true, but the problem is, protein (as is found in muscles) can be converted into glucose to fuel activity as well! This process is even easier than burning up bodyfat!
The question then becomes, is the extra fat burning you get worth the potential loss of muscle protein?

But there's more...

Another thing we have to consider is Growth Hormone. When you train on low-blood sugar conditions, your body releases increased amounts of GH. It sees these conditions as an emergency and responds with GH. GH has protective effects on muscle and improves the use of fat for energy. GH is not secreted in response to low-intensity activity - it's only significantly released by high intensity activity.

So, in theory, training with high intensity on an empty stomach first thing in morning can result in increased GH secretion, which means greater fat loss and reduced loss of muscle mass. This directly contradicts the theory of training burning up your muscle tissue if you don't eat.

Confused yet? Here's another monkey wrench...
Your cortisol levels are generally higher in the morning, simply because you've been fasting during the whole time you've been sleeping. Cortisol burns up muscle tissue and promotes fat storage.

And one last one, it's tough to train with intensity first thing in the morning! For best fat loss results, I always encourage high intensity interval training. If you're not a morning person (and I'm NOT!), it'll be tough to cardio with enough intensity to take advantage of the GH release.

MY SOLUTION:

My common-sense solution reads like a peace treaty... basically, if your primary goal is fat loss and you aren't too worried about losing a little muscle, go with empty stomach, high-intensity cardio training first thing in the morning. You may see increased fat loss, though you may lose a little muscle from it. Train with weights, and it probably won't be much loss at all.

If your goal is fat loss while preserving muscle as much as possible, take a small protein shake right after you wake up. THEN go do your cardio training. The protein will help spare your muscle tissue while not raising your blood sugar significantly enough to cause a problem.

Last thing...if you can't do your cardio with intensity first thing in the morning, do it later! That's my solution. Because truly, the absolute best time to do cardio is when you're energetic enough and alert enough to give it your best effort. THAT is when you'll really see results.

When you get right down to it, getting the most from your training, whether it be cardio or weights, is not about finagling over the details that won't make a difference in the long run. It's about digging in with intensity on a regular basis.

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Nick Nilsson is Vice-President of the online personal training company BetterU, Inc. He has a degree in Physical Education and Psychology and has been inventing new training techniques for more than 16 years. Nick is the author of a number of bodybuilding eBooks including "Metabolic Surge - Rapid Fat Loss," "The Best Exercises You've Never Heard Of," "Gluteus to the Maximus - Build a Bigger Butt NOW!" and "The Best Abdominal Exercises You've Never Heard Of" all available at (http://www.fitness-ebooks.com). He can be contacted at betteru@fitstep.com.