Food is fuel for your body. Just like cars can’t run without gas, your body can’t handle workouts properly without calories. Your body utilizes carbs and fats from food as the energy source when working out. Training on an empty stomach causes your body to go into a survival mode, saving the energy and making sure that fat doesn’t get burned away. The next time when you eat after such workout, your body will make up for the fat loss.
Working out on empty stomach won’t make you lose weight faster or speed up your metabolism. In fact, if your body doesn’t have any energy source, it will break down you muscle tissue. Fasting before working out puts a lot of stress on your body.
If you like to work out early in the morning, try to eat something before your training. You can drink a cup of juice or sweet tea or have something light like banana or cereal bar. It will give you some energy to power through your early morning workout.