Dear Sarah,

I am trying to lose weight. I am often think that if I go to the gym on an empty stomach that I will burn more calories. Is this true?

Maria

Dear Maria,

Working out on empty stomach is like trying to start your car without gasoline. You have to have glucose in your system to not only start your engine, but to keep it burning.

Glucose is the primary source of fuel during exercise, and it is derived from eating carbohydrates. Fats (triglycerides) are your secondary source of fuel and are stored in your fat cells.

More after the jump.

When you exercise on an empty stomach you reduce your blood and muscle glucose. Your brain is your control centre which runs on glucose. When the brain is unable to get glucose, the hormone cortisol will start to break down muscle. Your body goes into conservation mode and holds onto everything it can – especially fat.

You may burn some fats in this mode, however your fat stores will quickly be replenished once you eat.

To optimize your fat burning, you need to eat carbohydrates before exercise. The best form of carbohydrates to consume before a workout are fruits. Fruit can be easily digested to provide glucose in approximately 30 minutes. The best fruits are apples, bananas, grapefruit as they are low on the glycemic index and will provide sufficient glucose for a moderate (one hour) work out.

When your brain and body have enough glucose you will be able to access your secondary source of fuel, fat. It is important to remember that when you are looking to shed a few pounds, what matters is how many total calories you burn vs how many calories you take in.

Sarah Brown is a very healthy woman. She is not only a fitness instructor at Goodlife where she teaches Body Pump, Body Flow and yoga but she is also a registered holistic nutritionist. If you have a question for Sarah, leave a comment below and she will try and help, but note that not all questions will be answered.