From www.mercola.com Article by Doctor Mercola
Fasting Prior to Exercise Forces Fat Burning
You may have heard that exercising on an empty stomach will help burn more fat, and there seems to be some truth to that, although it might not be appropriate for everyone. Exercising vigorously when you’re blood sugar is low could lead to dizziness and poor performance, and exercising while hungry can also lead to overeating afterwards.
Personally, I believe the best approach is to use some common sense and listen to your body. For example, if you feel weak or nauseous while exercising on an empty stomach, you may want to at least eat a small meal before exercising.
That said, the reason why fasting before exercise seems to work is because the fat burning processes in your body are controlled by your sympathetic nervous system (SNS). The SNS is inherently activated by exercise and lack of food. The combination of fasting and exercising maximizes the impact of cellular factors and catalysts (cyclic AMP and AMP Kinases), which force the breakdown of fat and glycogen for energy. So, when you exercise on an empty stomach, you’re actually forcing your body to burn fat.
The Ideal Pre-Exercise Meal to Boost Fat Burning
A recent study found that consuming 20 grams of whey protein 30 minutes before resistance training can boost your body’s metabolism for as much as 24 hours after your workout.
It appears as though the amino acids found in high quality whey protein activate certain cellular mechanisms (mTORC-1), which in turn promote muscle protein synthesis, boost thyroid function, and also protect against declining testosterone levels after exercise.
In practical terms, consuming 20 grams of whey protein before exercise and another serving afterward will most likely yield the double benefit of increasing both fat burning and muscle build-up at the same time.
One of the worst foods you can eat prior to exercising is carbohydrates, as carbs will inhibit the SNS and reduce the fat burning effect of your exercise. Instead, this type of meal will activate your parasympathetic nervous system (PSNS), which promotes energy storage—the complete opposite of what you’re aiming for.
Personally I do strength training three times a week and will typically consume a whey protein meal one hour before, one hour after, and three hours after, to provide the fuel for muscle growth. This is not as necessary for non-strength training exercises, however.
I’m training for my 3rd Bodybuilding competition November 6th, the NPC Nevada Classic in the 50+ Masters Division. I’m in the process of getting down to 3% body fat for the competition. As Dr. Mercola says exercising on an empty stomach forces your body to burn fat. When you wake up you don’t have any glycogen (carbs) so the body uses fat for fuel immediately. I am doing one hour OF CARDIO first thing in the morning to burn fat. I always consume 40 grams of high quality protein about 30 minutes before working out (weight lifting) along with a nitric oxide product, which as pointed out helps for optimal muscle building and fat burning.