I do this every day. To be completely truthful my eating is not very good, I eat a lot of things I shouldn’t, but the fact that I train on an empty stomach every day makes it virtually impossible for me to gain fat.
So what should you do? Wake up, and train. Don’t eat breakfast or ANY calories. Why? Because when you eat something, your body will use that thing that you ate as fuel. The first thing it searches for as fuel is carbohydrates. What does this mean? Look at it this way, if I eat an apple and then I work out, what does my body use as fuel to get me through that workout? The apple. But if I work out on an empty stomach (I have slept for 6-8 hours, so the body has used up everything that I have eaten. It is digested, and used in carrying out various bodily functions) then there is nothing there for the body to burn, therefore the body (as it has found no carbs or other food nutrients to burn as fuel) has no other choice but to use the fat in my body to power it through the workout. Studies show that working out in the morning burns up to 3 times more fat as opposed to working out at any other time during the day.