As a certified San Diego personal trainer I was shocked when I overheard another trainer explaining to their client that in order for them to lose weight they would have to exercise first thing in the morning on an empty stomach. Many clients ask me about this phenomenon that has been flooding the fitness market. I am writing to clear this up once and for all.
Exercising on an empty stomach is probably the best way to have a weak, ineffective workout. Your body has gone 8+ hours without any food or water. So your blood sugar levels are extremely low and not sufficient to fuel your body through an entire workout.
The rumor is that working out on an empty stomach allows your body to only use fat stores as a source of fuel, so therefore all the calories you burn are fat because they are no immediate carbohydrate stores for your body to access. The more “fat” calories you burn the better, right?
Wrong. Eating first thing in the morning or before your workout in the afternoon actually helps rev up your body’s metabolism. Which means not only will you have more energy to push through your workout but you will also have an elevated metabolism meaning you will burn more calories overall. Your body will always use a combination of fat and carbohydrates as energy sources for the body. It will never choose one over the other no matter what time of day and when you last ate.
I suggest that you eat a small snack of carbohydrate and protein like cheese and crackers, or yogurt and granola an hour before your workout. If you are pressed for time, a glass of Gatorade or OJ will give you immediate carbohydrates to help fuel your workout.