Drink plenty of fluids and have a light snack 1 hour before training. When exercising, your body uses its glycogen i.e. sugar which is stored in the muscles and the liver. Eating a snack 1-2 hours before working out can help reduce the chance of you feeling lightheaded, dizzy, or nausea during exercise by giving your body a surplus of glycogen. If you are going to eat, eat an easy to digest meal such as oatmeal, a granola bar, or a little bit of rice.